<PRE><B>Question 1135518</B>
let x equal the number of gallons of 40 percent antifreeze.


100 * .20 + x * .40 = .35 * (x + 100)


simplify to get 20 + .40 * x = .35 * x + .35 * 100.


simplify further to get 20 + .4x = .35x + 35.


subtract 20 from both sides of this euation and subtract .35x from both sides of this equation to get .4x - .35x = 35 - 20.


simplify to get .05x = 15.


solve for x to get x = 300.


100 * .20 + 300 * .40 = 20 + 120 = 140.


140 / 400 = .35 * 100 = = 35%.


he will need 300 gallons of 40% antifreeze to mix with 100 gallons of 20% antifreeze to get 400 gallons of 35% antifreeze.


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