Input the fraction = 95/8
Integer =11
Fraction part = 7/8
Answer = 11.875
I think we need a coordinate grid for that,,
We are given this

write it as the difference of cubes

use the formula for the difference of cubes

Now use the formula for the difference of squares as 

140 if I observed the image correctly.
Answer:
You subtract because you're taking away money when you're withdrawing.