Work time math help
There are three groups, Group A has 6 efficient workers who can get a work done in 10 days. Group B has 8 moderately skilled workers who can get the same work done in 12 days. Group C has 10 low-skilled workers who can get the same work done in 15 days. Nine (9) workers are chosen, 2 from Group A, 5 from Group B and 2 from Group C. In how many days can these nine (9) workers get the job done? (please show all steps involved).