天山-6-26 怎么不会算了？

Q26

Running at their respective constant rates, machine X takes 2 days longer to produce W widgets than machine Y. At these rate, if the two machines together produce 5/4 W widgets in 3 days, how many days would it take machine X alone to produce 2W widgets?

A.4

B.6

C.8

D.10

E.12

答案是E， 可是我算了半天都是C。 谁能告诉我答案是怎么算出来的，谢谢！

真是糊涂啊，居然把5/4后面加上了W，怪不得！

谢谢！