Question 249334
How many gallons of a 10% salt solution should be added to 20 gallons of a 60% salt solution to obtain a 50% salt solution?

Let x be the number of gallons of 10% solution to be added. Then:

.6*20 + .1*x = .5*(20+x)
12 + .1*x = 10 + .5x
.4*x = 2
4*x = 20
x = ?