A type Q machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type Q machines and 3 type B machines working together and independently to complete the job?  Select.
A) 1/5 B) 29/35 C) 5/6 D) 35/29 E) 35/12
now D should be the answer.   Q need 5 hours to complete   and B needs 7 hours to compete   so 2Q + 3B will complete 2/5 + 3/7 or 29/35 portion of the job in 1 hour   so the whole job will take 35/29 hours....=35/29
<result>D</result>
A type Q machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type Q machines and 3 type B machines working together and independently to complete the job?