A chemist needs to mix an 18% acid solution with a 45% acid solution to obtain 12 liters of a 36% solution. How many liters of each of the acid solutions must be used?

Answer 1

.18 a + .45 b = .36 (a+b)
a + b = 12
so b = (12-a)
then
.18 a + .45 (12-a) = .36 [ a + (12-a) ]