what is the answer for this work problem

[rehab-299]

if X worked alone to take him 15 hours then y independently for18 hours if x alone to do first for 6 hours, two people were doing together for three hours, rest of job will be finished by y , and then y need how many hours to coplete?
A)13/3hours B)17/3hours C)13/5hours D)16/3 hours D)16/5 hours e)21/5 hours

[2amitprakash]

With few assumptions about spellings! Find the rates:
X - 1/15 of work in 1 hour
Y - 1/18 of work in 1 hour
So X+Y - (1/15 + 1/18 = 11/90) in 1 hour

Now how much work is done:
X did 6/15
X+Y did 11/30
Remaining work = 1-(6/15+11/30) = 7/30

So Y will take 18*7/30 = 21/5 hours. (E)

[Ben Ku]

Can you please re-type the question with the EXACT wording? It's unclear what is being stated in the question you posted. Thanks.

[coolbudy.samdarsh]

Rate of X=1/15
Rate of Y=1/18
Pick a magic number and take it as a dummy work amount.
magic number=LCM of 15 and 18=i.e. 90
=> Rate of X=6/hr
=> Rate of Y= 5/hr
work done by x alone in 6 hrs=6x6=36
work done by both x and y in 3 hrs=(6+5)x3=33
work left= 90-(36+33)=21
time taken by y to complete rest of the work=work left/rate of y => 21/5.
bingo!.

[jlucero]

That method works as well. Let us know if you have any questions.