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?

We can answer with fractions:

1/10 (Jack’s time) +x/15+x/12=1

Then we multiply everything by 15.

1 1/2+x+ 1 1/4x=15

Then we simplify:

2 1/4x=13 1/2

Then we divide both sides by 2 1/4x

x=6

1/10+2/5+1/2=1/10+4/10+5/10=1

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).

I hope this helps!