Let the work be of 40 units Amount of work done by Anil in one day =
40
20
=2 units Amount of work done by Sunil in one day =
20
20
=1 units Bimal does 10% work i.e. 4 units. Rest 40−4=36 units is done by Anil and Sunil. Let Anil took x days. Therefore, Sunil took (x−3) days. Therefore, 2×x+1×(x−3)=36 Or x=13 days.