How many quarts of pure antifreeze must be added to 7 quarts of a 20% antifreeze solution to obtain a 60% antifreeze solution

Answer 1

Let x = number of quarts of 100% antifreeze

1.00x + 0.20(7) = 0.60(x + 7)

x + 1.4 = 0.60x + 4.2

0.40x = 2.8

x = 7 quarts