Question

Estimate then find the difference or sum 86+17

Answer 1

Estimation for addition: 86 rounds up to 90 and 17 rounds up to 20 so:
90 + 20 = 110
Estimation for subtraction is the same thing but with subtraction
90 - 20 = 70

Now for the exact answers:
86 + 17 = 103
86 - 17 = 69

Your answers are 110, 70, 103, and 69.