Explain the concept of composing and decomposing 10 for addition with examples.

The strategy is to decompose one of the addends to compose a 10 with the other addend. Then, add the remaining part.

• For $8 + 3$: Decompose 3 into 2 and 1. Add 2 to 8 to make 10. Then add the remaining 1.

$$8 + 3 = 8 + (2 + 1) = (8 + 2) + 1 = 10 + 1 = \boxed{11}$$

• For $4 + 8$: Decompose 8 into 6 and 2. Add 6 to 4 to make 10. Then add the remaining 2.

$$4 + 8 = 4 + (6 + 2) = (4 + 6) + 2 = 10 + 2 = \boxed{12}$$

• For $6 + 7$: Decompose 7 into 4 and 3. Add 4 to 6 to make 10. Then add the remaining 3.

$$6 + 7 = 6 + (4 + 3) = (6 + 4) + 3 = 10 + 3 = \boxed{13}$$