if x is less than y by 20 % then y exceed x by :
using formula ( x / ( 100 - x ) * 100 ) where x is percentage decrease ( here it is 20 % ) = > 20 / ( 100 - 20 ) * 100 = 25 % answer : b
multiply(subtract(divide(const_100, subtract(const_100, 20)), const_1), const_100)