麻烦大侠们能解释一下这道弱智的DS的过程吗？

songxuebest

41.

Machines X and Y work at their respective constant rates.How many more hours does it take machine Y, working alone, to fill a production order of a certain size than it takes machine X, working alone?



(1) Machines X and Y, working together, fill a production order of this size in two-thirds the time that machine X, working alone, does.



(2) Machine Y, working alone, fills a production order of this size in twice the time that machine X, working alone, does.

我是设他们效率为X,Y，则
1/x+y = 2/3x   ,   1/y = 2/x
然后解方程吗？发现X=y，之后呢？