SOLUTION: A chemical company mixes pure water with their premium antifreeze solution to create an inexpensive antifreeze mixture. The premium antifreeze solution contains 85% pure antifreeze

Let x be the volume of the premium 85% antifreeze (in gallons) and

let y be the volume of water.


        x + y  = 170       gallons     (1)   (total volume equation)

    0.85x      = 0.15*170   gallons    (2)   (pure antifreeze volume equation)


From equation (2),  x =  = 30.


Then from (1),  y = 170-30 = 140 gallons.


ANSWER.  140 gallons of water.

Since they simply DILUTE the existing mixture, the content of the pure antifreeze remains the same: it is   = 25.5 gallons.


Hence, the 85% premium antifreeze should have the volume of   = 30 gallons to be 85% mixture.


The complement to 170 gallons, i.e.  170 - 30 = 140 gallons, is the water volume, which should be added.