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10.By weight, liquid A makes up 8 percent of solution R and 18 percent of solution S. If 3 grams of solution R are mixed with 7 grams of solution S, then liquid A accounts for what percent of the weight of the resulting solution?
A 10%
B 13%
C 15%
D 19%
E 26%
这个题小学也经常遇到，(3*8%+7+18%)/(7+3)=15%