Three grades of milk are 2 percent, 3 percent and 5 percent fat by volume. If x gallons of the 2 percent grade, y gallons of the 3 percent grade, and z gallons of the 5 percent grade are mixed to give x+y+z gallons of a 4 percent grade, what is x in terms of y and z? Choose the correct choice from the following choices.
A) y + 3z  B) (y +z) / 4  C) 2y + 3z  D) z/2  E) 3y + 4.5z
Based on the given information, the following equation could be dervied: 2% * x + 4% * y + 5% * z = 4% * (x+y+z) Then use algebra to figure out -2%*x = 0%*y - 1%*z. Thus, 2x = z.   z/2
<result>D</result>
Three grades of milk are 2 percent, 3 percent and 5 percent fat by volume. If x gallons of the 2 percent grade, y gallons of the 3 percent grade, and z gallons of the 5 percent grade are mixed to give x+y+z gallons of a 4 percent grade, what is x in terms of y and z?