Math Question - Algebra

Question

A service station checks Mr. Gittleboro's radiator and finds it contains only 30% antifreeze. If the radiator holds 10 quarts and is full, how much must be drained off and replaced with pure antifreeze in order to bring it up to a required 50% antifreeze?

Answer 1

Let x be the amount removed and then replaced with pure (100%) antifreeze

(10-x)*.3 +x =.5*10

3 -.3x + x = 5

.7x=2

x=20/7 qts