求一道简单的题，但是我就是搞不懂。

The charge for a single room at Hotel P
is 25 percent less than the charge for a single room at Hotel R and 10
percent less than the charge for a single room at Hotel G.  The charge for a single room at Hotel R
is what percent greater than the charge for a single room at Hotel G ?

A.       15%

B.       20%

C.       40%

D.       50%

这道题选B，但是我算出来是1/6。

E.      150%

设P R G的charge分别为p r g  则依题意

p=0.75r

p=0.9g

推出r=4p/3   g=10p/9

答案为r-g/r =0.2

不知道这么解释行否 

是：(r-g)/g=0.2