求高人指点, GMAT 数学 OG12 223

题目

求高人指点, GMAT 数学 OG12 223
Seed mixture X is 40 percent ryegrass and 60 percent bluegrass by weight;seed mixture Y is 25 percent ryegrass and 75 percent fescue.If a mixyure of X and Y contains 30 percent ryegrass, what percent of the weight of the mixture is X?
A 10%
B 33又 3 分之1 %
C 40%
D 50%
E 66 又 3 分之2%
答案是C ,算不出来.
求帮忙.

答案