Question

a and b can do a piece of work in 12 days, b and c in 15 days and c and a in 20 days. how much time will a alone take to finish the job

Answer 1

A and b can do a piece of work in 12 days. If a alone have to finish the job among b and c so

A and b=12
A (24 days alone without b)

So if b and c 15 days and c 20 days. If a have to do all I would add 24 and 15 and 20 which would be 59 days