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Any number between 1 and 9 plus 10 is just that number but with a 1 in in front, as if you dropped the zero from 10 and replaced it with the number. (Ex: 10 + 6 = 16) With numbers besides 1-10, like 7 + 13, you can think, "7 + 3 = 10, and 13 - 3 = 10. So if i took the 3 from 13 and give it to the 7, I'd have 10 + 10 = 20!" Or:

7 + 13

-3

10

7 + 10 = 17

+3

20

If this doesn't make sense, try really thinking about my answer. I hope helped! If you have any questions about this just ask and I'll answer.

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