Question

A and b can do a piece of work in 7 days. with the help of c they finish thework in 5 days. c alone can do that piece of work in?

Answer 1

let work done by a and b be x
work done by c be y
x=1/7
x+y=1/5
1/7+y=1/5
y=1/5-1/7
y=2/35
c does work in 35/2 days alone