We need 84 gallons of 3% butterfat milk and (84 * 3) = 252 gallons of 7% butterfat milk to obtain 336 gallons of 6% butterfat milk.
Let x = number of gallons of 3% milk
Thus;
336 - x = number of gallons of 7% milk
Therefore;
0.03x + 0.07(336 - x) = 0.06(336)
0.03x + 23.52 - 0.07x = 20.16
-0.04x = -3.36
x = 84 gallons
We need 84 gallons of 3% butterfat milk and (84 * 3) = 252 gallons of 7% butterfat milk to obtain 336 gallons of 6% butterfat milk.
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