How much water must be added to 5 qt of a 45% antifreeze solution to dilute it to a solution that is 35% antifreeze? show work : )

We have 5 quarts of 45% antifreeze to which we will add "x" quarts of water to make a 35% antifreeze solution.
How many quarts of water do we add?
.45 * 5 + 0*x = .35 * (5 +x)
2.25 + 0x = 1.75 + .35x
.5 = .35x
x = 1.4285714286
So we need to add 1.43 quarts of water.

Double Check
We START with a solution of 2.25 quarts of antifreeze and 2.75 quarts of water.  We add 1.43 quarts of water making a solution with a volume of 6.43 quarts. 
The final solution is 2.25 quarts of antifreeze plus (2.75 + 1.43) or 4.18 quarts of water for a 6.43 quart total.
2.25 / 6.43 = 35% antifreeze.
4.18 / 6.43 = 65% water.
correct !
(You might find this page quite helpful:)
http://www.1728.org/mixture.htm