what is the % change in the area of a rectangle when its length increases by 20 % and its width decreases by 20 % ?
"( 12 / 10 ) * ( 8 / 10 ) = 96 / 100 of original area 96 / 100 is a 4 % decrease from 100 / 100 - > d"
subtract(const_100, divide(multiply(add(const_100, 20), subtract(const_100, 20)), const_100))