Working individually, Allison can sew dresses for 9 hours and Al can sew dresses in 12 hours. If Allison and Al work together but independently at the task for 3 hours, at which point Al leaves, how many remaining hours will it take Allison to complete the task alone?
Answers:
A) 45/12
B) 23/12
C) 40/33
D) 34/12
E) 43/5
In first 3 hrs Al will finish 3/12 = 1/4 of work and Allison will finish 3/9=1/3 work so total 1/4 + 1/3 = 7/12 work is finished and 1-7/12 = 5/12 work remaining. Now Allison will take (5/12)*9 = 45/12 hrs to finish it.   So answer is 45/12.
<result>A</result>
Working individually, Allison can sew dresses for 9 hours and Al can sew dresses in 12 hours. If Allison and Al work together but independently at the task for 3 hours, at which point Al leaves, how many remaining hours will it take Allison to complete the task alone?