A father can do a certain job in x hours. His son takes twice as long to do the job. Working together, they can do the job in 6 hours. How many hours does the father take to do the job?  Choose the correct choice from the following answers:
A) 9
B) 18
C) 12
D) 20
E) 16
Explanatory Answers   The father completes the job in x hours.   So, the son will take 2x hours to complete the same job.   In an hour, the father will complete 1/x of the total job.   In an hour, the son will complete 1/2x of the total job.   So, if the father and son work together, in an hour they will complete 1/x + 1/2x of the job.   i.e., in an hour they will complete 3/2x of the job.   The question states that they complete the entire task in 6 hours if they work together.   i.e., they complete 1/6<sup>th</sup> of the task in an hour.   Equating the two information, we get 3/2x = 1/6   Cross multiplying and solving for x we get 2x = 18 or x = 9.   The father takes 9 hours to complete the job.   9nswer 9
<result>A</result>
A father can do a certain job in x hours. His son takes twice as long to do the job. Working together, they can do the job in 6 hours. How many hours does the father take to do the job?