ted, sam, and jack can do a piece of work in 15, 12 and 20 days respectively. they started the work together, but jack left after 2 days. in how many days will the remaining work be completed by ted and sam?
So Ted and Sam will take 4 remaining days to finish the work. (6 total days including Jack minus the 2 days he spent working gets you 4 days with just Ted and Sam).