Question

please solve this immediately withproper steps and discription

Answer 1

work done by a per day=1/9
work done by b per day =1/12
working on alternative days, 1/9+1/12 work I'd completed on 2 days.
=21/108
in 10 days, 105/108 work will be done
on the 11th day, a fill finish the work.