How many gallons of a 60 antifreeze solution must be mixed w
     How many gallons of a 60% antifreeze solution must be mixed with 80 gallons of 15% antifreeze to get a mixture that is 50 antifreeze? Use the six-step method  You need  gallons.  (Round to the nearest whole number) 
  
  Solution
Answer: 380 gallons (As explained below)
Let \'x\' be the gallons of 60% antifreeze solution to be mixed. Then,
(0.6)(x) + (0.15)(80) = 0.5(100 + x)
 0.6x + 12 = 50 + 0.5x
 0.6x - 0.5x = 50 - 12
 0.1x = 38
 x = 35 / 0.1 = 380 gallons.

