How many gallons should be mixed?

Question

A 20​% solution of fertilizer is to be mixed with a 70​% solution of fertilizer in order to get 100 gallons of a 60​%

solution. How many gallons of the 20​% solution and 70​% solution should be​ mixed?

Answer 1

Let T=gal of 20% and S=gal 70%

T + S =100

.2T + .7S = .6*100

2T + 2S = 200

2T + 7S = 600

5S=400

S=80

T=20