For Part A, the doubles fact that will help Tia find the sum of 4 + 5 is 4 + 4 = 8. This is because 5 is one more than 4, so she can use the fact that 4 + 4 is 8 and add one more.
For Part B, the sum of 4 + 5 is 9.
So,
- Part A: 4 + 4 = 8
- Part B: 4 + 5 = 9