Assistance on Algebra word problem

Tomaslav has learned the following facts well:

All the sums of whole numbers that add to 10 or less-Tomaslav knows these facts "forwards and backwards." For example, he knows not only that 5+2 is 7 but also that 7 breaks down into 5+2 or 2+5.

- 10+1,10+2,10+3,...,10+10
- the
*doubles* 1+1, 2+2, 3+3,...,10+10

For each sum in the problem, describe at least three different ways that Tomaslav could use reasoning, together with the facts he knows well, to determine the sum. In each case, write equations that correspond to the strategies you describe. Use parentheses appropriately if needed

a. 8+7

b. 6+7

c. 8+9 (Find four ways to solve this problem only)