A can do a piece of work in 5 hours; B and C together can do it in 4 hours, while A and C together can do it in 3 hours. How long will B alone take to do it? Select:
A) 60/7 hours B) 70/6 hours C) 35/2 hours D) 90.8 hours E) none of the above
A's 1 hour's work = 1/5 ;   (B + C)'s 1 hour's work = 1/4 ;   (B + C)'s 1 hour's work = 1/3   (A + B + C)'s 1 hour's work = (1/5 + 1/4) = 9/20   B's 1 hour's work = (9/20 - 1/3) = 7/60   B alone will take 60/7 hours to do the work.   60/7 hoursnswer = 60/7 hours
<result>A</result>
A can do a piece of work in 5 hours; B and C together can do it in 4 hours, while A and C together can do it in 3 hours. How long will B alone take to do it?