Twelve men can complete a work in 8 days. Three days after they started the work, 3 more men joined them. In how, many days will all of them together complete the remaining work

1 men's one day's work = 1/96
12 men's 3 day's work = 3 x (1/8) = 3/8
Remaining work = (1 - 3/8) = 5/8
15 men's 1 day's work = 15/96
Now, 15/96 work is done by them in 1 day
∴ 5/8 work will be done by them in = (96/15) x (5/ 8) i.e., 4 days