Question

X and Y can do a piece of work in 20 days
and 12 days respectively. X started the work
alone and then after 4 days Y joined him til
the completion of the work. How long did the
work last?
(A) 6 days
B) 10 days
(C) 15 days
(D) 20 days​

Answer 1

Answer:

6, is the answer but I am not sure