A and B can finish a work in 20 days. A alone can do 1/5th of the work in 12 days. In how many days can B alone do it?

Explanation

A and B's one day work =`'1/20'`
A's `'12'` days work =`1/5`
A's `1` days work =`1/5` `xx``1/12`
=`1/60`
Then B's 1 day work =`1/20 -1/60`
=`1/30`
∴B can do the work in
=`30` days.