Question 751178
How many gallons of a 10% antifreeze solution: 0.10x 
and a 25 % Antifreeze solution must be mixed: 0.25y 
to make 3 gallons of a 20 % antifreeze solution: (3)(0.20)=0.6


but x+y=3 (so y=3-x)

and we write



0.1x+0.25(3-x)=0.6

which gives us x=1 gallon




:)