gwd-11-36

uspresident

Q36:If x, y, and k are positive numbers such that [x/(x+y)](10) +[y/(x+y)](20) = k and if x < y, which of the following could be the value of k?

A. 10

B. 12

C. 15

D. 18 x=2,y=8

E. 30

这个题我是凑数字的，正常应该怎么算？