Answer:
0.5 pounds of butter.
Explanation
X pounds for 0.25 gallons.
0.5 gallon of cream - 1 pound of butter
0.25 gallons of cream - X pounds of butter
Applying cross multiplication:
0.5X = 0.25
X = 0.25 over 0.5 or 0.25/0.5
X = 0.5
Therefor, you could make 0.5 pounds of butter with 0.25 gallons of cream.
Just plug in one of the other (doesn't matter which one) so it will look like
-3x+6=5x+38
or
5x+38=-3x+6 (it's the same thing as the first one)
Then you solve for x and you substitute that value so you can get y.
Hope this helped :)
Step 2! The reason for that is the student didnt multiplied (15-2z) with -2. But she should have!