Question 464459
1/t+1/t+10=1/12
12(t+10)+12t=t(t+10)
12t+120+12t=t2+10t
t2-14t-120=0
(t-20)(t+6)=0
t=20 or -6
Throwing out the negative answer we get the larger pipe taking 20 minutes, and the smaller pipe taking t+10, or 30 minutes..