Addition Level 1

All images from Openclipart.org / Creative Commons Zero 1.0 License

Addition Level 2

All images from Openclipart.org / Creative Commons Zero 1.0 License

Subtraction Level 1

1. Public domain / Piotr Siedlecki (publicdomainpictures.net)
3. Public domain / https://freesvg.org
4. CC0 1.0 Universal (CC0 1.0) / publicdomainpictures.net
5. Pixabay.com / gvozdenivan
7. Openclipart.org / Creative Commons Zero 1.0 License
8. www.maxpixel.net / Creative Commons Zero - CC0.
9. Openclipart.org / Creative Commons Zero 1.0 License
10. Openclipart.org / Creative Commons Zero 1.0 License

Subtraction Level 2

2. https://freesvg.org / Creative Commons
3. Openclipart.org / Creative Commons Zero 1.0 License
4. Free-vectors.net / Attribution 4.0 International (CC BY 4.0)
7. Openclipart.org / Creative Commons Zero 1.0 License
8. Openclipart.org / Creative Commons Zero 1.0 License
9. Openclipart.org / Creative Commons Zero 1.0 License
10. Pixnio / Creative Commons CC0

Division Level 1

1. Openclipart.org
2. Openclipart.org
3. Openclipart.org
4. Publicdomainpictures.net / CC0 Public Domain
6. Openclipart.org
7. Pikist.com
9. Openclipart.org
10. Openclipart.org

Division Level 2

2. Openclipart.org
3. Photo via Good Free Photos
4. Public domain
5. www.pxfuel.com
6. Openclipart.org
7. Openclipart.org
8. Openclipart.org
9. Pixnio.com / Public domain
10. Needpix.com / Public domain

Multiplication Level 1

1. www.pikist.com
2. Openclipart.org
3. Openclipart.org
4. Openclipart.org
5. Pixabay / Public domain
6. Openclipart.org
7. Openclipart.org
8. CC0 Public Domain / Publicdomainpictures.net
9. Openclipart.org
10. Pixabay / Public domain

Multiplication Level 2

1. CC0 Public Domain
2. Openclipart.org
3. Openclipart.org
4. Creative Commons Attribution-Share Alike 3.0 / Lindy Neefjes
5. CC BY-SA 2.0 / Flickr.com / Paul
6. Openclipart.org
7. Flickr.com / Sage Ross
8. CC0 Public Domain / Maxpixel.net
9. Image credit: : Public Domain / Rawpixel
10. Openclipart.org

Roman numerals

1. Reinhold Möller (CC BY-SA 4.0)
2. CC BY-SA 2.0 / Michael Coghlan / flickr.com
3. Humphrey Bolton / CC BY-SA 2.0
5. Pixabay
6. Creative Commons Attribution 2.5 au / JarrahTree
9. Copyright Jaggery and licensed for reuse under CC BY-SA 2.0
10.  CC BY-SA 3.0 / Wolfgang Sauber

Telling the time Level 1

7. pixabay.com

Telling the time Level 2

4. Pxfuel.com
7. Openclipart.org / Creative Commons Zero 1.0 License
10. Openclipart.org / Creative Commons Zero 1.0 License

Fractions Level 1

1. Openclipart.org / Creative Commons Zero 1.0 License
2. Pixabay / public domain
4. Openclipart.org / Creative Commons Zero 1.0 License
5.  Creative CommonsAttribution 2.5 Generic license. / Ian Tresman
6. Openclipart.org / Creative Commons Zero 1.0 License
7. Openclipart.org / Creative Commons Zero 1.0 License
8. Openclipart.org / Creative Commons Zero 1.0 License
9. Openclipart.org / Creative Commons Zero 1.0 License

Fractions Level 2

1. Attribution-Share Alike 3.0 Unported / Apamodp
4. Openclipart.org
5. Flickr.com / Mikelo /  Creative CommonsAttribution-Share Alike 2.0 Generic license.
6. Open Clip Art Library / Public Domain + Needpix.com / Public Domain
7. CC BY-SA 2.0 / Flickr.com / Ian Barbour
8. Flickr.com / Robert Couse-Baker / CC BY 2.0
9. Openclipart.org
10. Openclipart.org

Algebra

1. Creative Commons 2.0 / source
2. CC0 Public Domain / https://pxhere.com/en/photo/1355988
5. Creative Commons 1.0 
6. Openclipart.org
7. Creative Commons 2.0  / Alex Proimos
8. Pixnio / Creative Commons 0 
9. Creative Commons 2.0 / source

Volume and capacity

1. CC0 Public Domain / Pixabay.com
2. Openclipart.org
3. Openclipart.org
4. Openclipart.org
5. Openclipart.org
6. CC0 Public Domain / PXHERE.COM
7. Pixabay.com
8. Openclipart.org
9. Openclipart.org
​​​​​​​10. Openclipart.org

Mass and weight

1. Openclipart.org
2. Openclipart.org
3. Openclipart.org
​​​​​​​4. CC BY-SA 4.0 / Pixabay.com
5. CC0 Public Domain / pxhere.com
6. Openclipart.org
7. Openclipart.org
8. Openclipart.org
9. Openclipart.org
​​​​​​​10. Openclipart.org

2D shapes

3. CC0 Public Domain
9. CC0 Public Domain

3D shapes

1. Openclipart.org
2. CC0 Public Domain / maxpixel.net
3.  Creative Commons Attribution-Share Alike 4.0 International license / Tomruen
4. CC0 Public Domain
5. Public domain
6.  Creative CommonsAttribution-Share Alike 3.0 Unported / Ssawka
9. Openclipart.org

Symmetry

9. Openclipart.org

Ratio

1. Pixabay
2. Openclipart.org
3. Openclipart.org
4. Openclipart.org
10. Openclipart.org

Pythagoras' theorem

7. Openclipart.org
9. Openclipart.org
10. Openclipart.org

Angles

1. Maxpixel.net / Creative Commons Zero - CC0
7. Pickpic.com
8. Openclipart.org
9. Openclipart.org

Area

1. Openclipart.org
4. Public domain / pxfuel.com
5. CC BY-SA 2.0 / Flickr.com / Ian Muttoo
10. MALIZ ONG (publicdomainpictures.net)

Money

£ all coins - istockphoto.com
£ all notes - public domain

7. Public domain / https://www.pxfuel.com/
8. Openclipart.org / public domain
9. £s - publicdomainvectors.org

Graphs

8.  Creative CommonsCC0 1.0 Universal Public Domain Dedication

Coordinates

1. Creative Commons 2.0 / Source
2. Creative Commons 1.0
3. Openclipart.org
4. Creative Commons 2.0  / Alex Proimos
5. Pixnio / Creative Commons 0 
6. CC0 Public Domain / Source
9. Creative Commons 2.0 / Source

Multiples

2. Openclipart.org
6. CC0 Public domain / Rawpixel.com
9. https://www.peakpx.com

Probability

2. Creative CommonsAttribution-Share Alike 2.0 Generic / ICMA Photos
3. CC0 Public Domain / Joy Shrader
4. Openclipart.org
5. CC0 Public Domain
6.  CC BY-SA 3.0 / Attribution / Nick Youngson / Original Image
7. Openclipart.org
​​​​​​​8. Openclipart.org
10. Openclipart.org

Average

1. CC BY 2.0 / Flickr.com / Wendy Berry
2. Openclipart.org
3. Openclipart.org
4. CC BY 2.0 / Roman Boed
5. CC 0 / Public domain
8. Openclipart.org
9. CC BY-SA 2.0 / Flickr.com / JJ Merelo

Circles and pi

3. Openclipart.org
4. CC BY-SA 2.0 / Flickr.com / Neil Cummings
7. Pinterest / David Stone
9. CC0 1.0
10. Creative CommonsAttribution-Share Alike 3.0 / Cmglee

Rounding decimals

2. CC0 Public Domain
3. CC0 Public Domain
5. openclipart.org
6. CC BY 2.0 / Flickr.com / Eirik Newth
7. CC0 Public Domain
8. CC0 Public Domain
9. openclipart.org
Thumbnail - cc-by-2.0 / Flickr.com / Striegel

Decimals Level 1

1. Openclipart.org
2. Openclipart.org
3. Openclipart.org
4. Openclipart.org
6.  Creative CommonsAttribution-Share Alike 4.0 International / PPP
7. Openclipart.org

Decimals Level 2

1. Openclipart.org
2. https://gallery.yopriceville.com/var/resizes/Free-Clipart-Pictures/Fast-Food-PNG-Clipart/Pizza_PNG_Image.png?m=1507172108
3. Openclipart.org
4. CC BY 2.0 / Flickr.com / Kimberley Vardeman
5. Publicdomainvectors.org / public domain
6. Publicdomainvectors.org / public domain
7.  Publicdomainvectors.org / public domain
8. Image by rawpixel.com
9. Credit: rawpixel.com
10. CC0 Public Domain

Place value

​​​​​​​5. CC BY-SA 2.0 / Adam Ward / https://www.geograph.org.uk/
6. Openclipart.org
7. CC 3.0 / Spaicecowboi / Source

Percentages

1. Image credit: Q-files.com created
2. Image credit: CC BY 2.0 / Flickr.com: Sarah Shuda
3. Image credit: Clipart
4. Image credit: CC BY 2.0 / Flickr.com: Homes For Pets
5. Image credit: CC BY 2.0 / Flickr.com: King of the Vegetables
6. Image credit: CC BY 2.0 / Flickr.com: Sarah Stierch
7. Image credit: CC BY 2.0 / Flickr.com: Ryan Tracey
8. Image credit: Public domain
9. Image credit: CC BY 0.0 / Public Domain
​​​​​​​10. Image credit: Pixabay.com

Negative numbers

1. Image credit: Q-files
2. Image credit: Q-files
3. Image credit: Quant / CC BY-SA 3.0
4. Image credit: www.pxfuel.com
5. Image credit: RickybanPhotography / Flickr.com/ CC BY 2.0
6. Image credit: Secret Pilgrim / Flickr.com / CC BY 2.0
7. Image credit: U.S. D.O.D. graphic by Ron Stern / Public domain
8. Image credit: karlnorling from Brooklyn, USA / CC by 2.0
9. Image credit: Q-files.com
10. Image credit: U.S. Air Force photo by Kemberly Groue / Public domain