Brix in Wine Making problem..?

You currently have 3 liters of a solution of Bx-11, which means you have 330 grams of sugar in 3L of solution. What you want is 4 liters @ Bx-20. That means you'll need 800 grams of sugar in 4L of solution. Accordingly, you'll need 470 grams of sugar dissolved in one liter of water.