Question

A can do a certain job in 4 days and with B's assistance he can do the same job in 12/7 days. how long will B take to finish the job working alone?​

Answer 1

7/12–1/4=7/12–3/12=4/12=1/3

B takes 3 days, working alone.

1/3 + 1/4=3+4/12=7/12

1/ 7/12=12/7