Three grades of milk are 1 percent, 5 percent and 3 percent fat by volume. If x gallons of the 1 percent grade, y gallons of the 5 percent grade, and z gallons of the 3 percent grade are mixed to give x+y+z gallons of a 7 percent grade, what is x in terms of y and z?\nOptions:\n(A) -1y - 2z\n(B) (y +z)  / 4\n(C) 2y + 3z\n(D) 3y + z\n(E) 3y + 4.5z Hmmm, my stream of consciousness:
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Based on the given information, the following equation could be dervied: 1% * x + 5% * y + 3% * z = 7% * (x+y+z)\nThen use algebra to figure out 6%*x = -2%*y - 4%*z. Thus, 3x = -1y - 2z. So, the answer is (A).
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