How many quarts of pure antifreeze must be added to 6 quarts

How many quarts of pure antifreeze must be added to 6 quarts of a 10% antifreeze solution to obtain a 20% antifreeze solution? quart(s) of pure antifreeze must be added. (Round to the nearest tenth as needed)

Solution

let x quarts of pure antifreeze be added

setting up the equation

x + .10 (6) = .20(6+x)

x + .6 = 1.2 + .20x

x - .20x = 1.2 - .6

.80 x = 6

x = 0.75

hence,

0.8 quarts of antifreeze must be added