[求助]OG11 数学PS 91.

If sam were twice as old as he is, he would be 40 years older than jim.If jim is 10years younger than sam,how old is sam?

不明白题干里的he指的是？

这是我列的式子：

设he的年龄是x，则sam是2x，jim是x-40

所以（x-40）+10=2x，得x=-30

是题干理解错了吗？