Fact Families
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OK, this is big stuff here...  The key to getting your addition and subtraction and being able to use them in bigger math problems later on is to see how addition and subtraction fit together!  These are called number families.

Look at these numbers:

2, 7, 9

What are four ways we can put these numbers together?

We get two with addition* and two with subtraction:
2+7=9 9-2=7
7+2=9 9-7=2

*Parents: Knowing both ways for addition will help when they learn things like the commutative property.