Answer
-26+4
Usuahaushbsbwjwjaja
Well, variables are stuff like x and y because they can represent a number. They are variable in an equation. so if you have (3x^3)+(5X^2)+Y+9 then your variables are x X and Y (im assuming the capital X is there and not a typo) if that was a typo and meant to be lowercase, then its just a 2 variable with the x and y
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.