Answer:
x=y+3z
Step-by-step explanation:
If we mixed the three grades of milk, the total percentage of fat by volume is given by:
(1%*x)+(2%*y)+(3%*z)
Where x is the number of gallons of 1% grade, y is the number of gallons of 2% grade and z is the number of gallons of 3%
We want that these percentage be equal to 1.5% of the total volume, so we create the following equation:
1.5%( x + y + z ) = (1%*x) + (2%*y )+ (3%*z)
Solving for x, we get:
1.5%*x + 1.5%*y + 1.5%*z = 1%*x + 2%*y + 3%*z
1.5%*x - 1%*x = 2%*y + 3%*z - 1.5%*y - 1.5%*z
0.5%*x = 0.5%*y + 1.5%*z
x = y + 3z
Then x in terms of y and z is x=y+3z