A can do a piece of work in 10 hours; B and C together can do it in 9 hours, while A and C together can do it in 18 hours. How long will B alone take to do it?	Choose the correct option
A) 5 5/4 hours B) 6 5/8 hours C) 15 8/6 hours D) 6 8/9 hours E) 6 6/14 hours
A's 1 hour's work = 1/10 ;   (B + C)'s 1 hour's work = 1/9 ;   (B + C)'s 1 hour's work = 1/18   (A + B + C)'s 1 hour's work = (1/10 + 1/9) = 19/90   B's 1 hour's work = (19/90 - 1/18) = 14/90   B alone will take 90/14 hours to do the work.   =6 6/14   Answer = 6 6/14 hours
<result>E</result>
A can do a piece of work in 10 hours; B and C together can do it in 9 hours, while A and C together can do it in 18 hours. How long will B alone take to do it?