Anuj & Bhanu finish the work in 30days.
In 20 days they have finished 20/30= 2/3 of work
The work left was 1-2/3=1/3
Anuj finished the work 1/3 work in 20 days
Anuj would finish the whole work in 1*20/(1/3)=60 days.
alone Anuj would finished the work in 60days.