Im pretty sure it would be 10??? if you are putting it as a subtraction problem if not i would try wording it more clearly
We know that
The mixture in Tank A is 5/(5+10) = 1/3 pure alcohol.
The mixture in Tank B is 3/(3+12) = 1/5 pure alcohol.
We want to combine these to make a mixture that is 25% = 1/4 pure alcohol.
Let
x------------------> the volume in gallons of solution taken from Tank A.
y------------------>the volume in gallons of solution taken from Tank B
Then
the volume taken from Tank B will be y=(8 -x)
remember that we are making a total of 8 gallons of solutions.
The alcohol content of the mixture is(1/3)x +(1/5)(8 -x) = (1/4)*85x + 3(8 -x) = 30 ----------> 5x+24-3x=30----------> 5x-3x=30-24
2x = 6 ----------------> x=3
y=8-x--------> y=8-3-----> y=5
the answer is
3 gallons should be taken from Tank A;
5 gallons should be taken from Tank B
You can subtract 78.2 from 287 to get the x value alone. Your new expression will look like this:
.5x=208.8
Next you divide by .5 (or multiply the reciprocal 1/.5 depending on how you were taught)
x=417.6
Hope that helps!!
