if A and B can do a piece of work in 10 days and A alone can do it in 15 days, how long will B take to do it?  Choose the correct choice.
A) 20	B) 30	C) 35	D) 40	E) 45
1/10-1/15=1/30   30 days   ANSWER:30
<result>B</result>
if A and B can do a piece of work in 10 days and A alone can do it in 15 days, how long will B take to do it?