Question

A and B together can finish a piece of work in 12 days if Aalone can finish the same work in 20 days how many days B alone can finish it

Answer 1

(A+B)'s one day work = 1/12th part
A's 1 day work= 1/20th part
B's 1 day work= 1/12-1/20 = (5-3)/60 = 2/60 = 1/30th part
B can finish work in 1/1/30 = 30 days

Answer 2

a+b)'s 1 days work= 1\12
and and b one day work=1/20
is 1 days work equal to a + b one day work - b one day work
=(1/12-1/20)=2/60=1/30
B alone can finish the work in 30 days