11 qt radiator is currently full of 30% anti-freeze. It is supposed to be 50%. How much should he drain out and replace with 100%.. continued below

Question

Full story problem.. Bob's 11-quart radiator is currently full of 30% anti-freeze. It is supposed to be 50%. How much should he drain out and replace with 100% anti-freeze to have a full radiator that is 50% antifreeze? 

 

 

 

Desperately need help with this mixture problem, all the numbers confused me, how would one set this up to get the equation and the correct answer? 

Answer 1

x represents the amount removed/replaced

0.3(11 - x) + x = 0.5(11)

3.3 - 0.3x + x = 5.5

3.3 + 0.7x = 5.5

0.7x = 2.2

x ≈ 3.14