Answer:
Both 8 gallons!
Explanation:
Let's say we have x gallons of 25% solution and y gallons of 45% solution.
Then, obviously, x+y=16.
But how much alcohol do we have? That will be 35% of 16 = 5.6
So the second equation you can create is:
0.25x + 0.45y = 5.6
Solve these together and you have your answer.
Let's do the second one times 4 to get integers:
0.25x + 0.45y = 5.6 =>
x + 1.8y = 22.4
Combine with the first:
22.4-1.8y + y = 16
0.8y = 6.4
y = 8
so x = 16-y = 8