Question 399355
a chemist has two solutions of the same acid, one containing 15% of the acid and the other 25%. how many cubic centimeters of each should he use to make 120 cc of a 21% acid solution?

15%.................x cc
25%.................120-x cc
21%................. 120 cc 
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15x+25(120-x)=21*120
15x+3000-25x=2520
-10x=-480
/-10
x=48 cc of 15% 
120-x====>120-48=72 cc
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