How many gallons of a 70% antifreeze solution must be mixed with 90 gallons of 30% antifreeze to get a mixture that is 60% antifreeze?
Let the number of gallons of 70% antifreeze needed = A
0.7A + 0.3*90 =0.6[A + 90], solve for A
A = 270 gallons of 70% antifreeze
