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
E. 30
A. 10
B. 12
C. 15
D. 18
E. 30
Is it D.
Given equation can be reduced to (10-k)x = (k-20)y
From here, I used back-solving. Only D satisfies the condition X<Y
