Question

a and b together working on alternate days can finish a piece of work in 17 days

Answer 1

 and B can finish a work, working on alternative days, in 17 days, where A works on the first day. Similarly they can finish the work, working on alternate days, in 53/3 days, where B works on the first day. C, working alone, can complete the work in 35 days. In how many days can the work be completed when A, B, and C work together?

A and B can finish a work , working on alternative days,in 17 days, where A works on the first day. 

ok as A first starts, then B