Question

How much pure antifreeze must be added to 12 gallons of 20% antifreeze to make a 50% antifreeze solution?

Answer 1

First of all, this belong's to the Chemistry section.

Then, we know that the formula for these kind of thing is C1V1 = C2V2
C1 = 20%
C2 = 50$
V1 = 12 gallons
V2 = x gallons

Once you'll get the # of gallons, you can find the amount of pure antifreeze by doing 50%*x.

Answer 2

3/5 * 12 = ...