How much of 20% alcohol solution and 50% alcohol solution must be mixted to get 9 liters of 30% alcohol solution?

Answer 1

I think it is 3.86 liters you should double check.

Answer 2

Jake, don't just state an answer, which is wrong anyway

amount of the 20% stuff --- x
amount of the 50% stuff --- 9-x

.2x + .5(9-x) = .3(9)
times 10
2x + 5(9-x) = 27
2x + 45 - 5x = 27
-3x = -18
x = 6

So he needs 6 L of the 20% solution, and
3 L of the 50% solution