15/7 is the best number which completes both equations.If 5/7Ă·1/3 then it becomes 5/7 X 3/1 where 1/3 in denominator becomes 3/1 so that the value is 15/7 then 15/7 multiplied by 1/3 which yields 5/7.So we derive the final answer 5/7.This result involves only simple multiplication and division.