Question

Three grades of milk are 1 percent, 2 percent, and 3 percent fat by volume. if x gallons of the 1 percent grade, y gallons of the 2 percent grade, and z gallons of the 3 percent grade are mixed to give x + y + z gallons of a 1.5 percent grade, what is x in terms of y and z ?

Answer 1

(1x+2y+3z)/(x+y+z)=1.5
x+2y+3z=1.5x+1.5y+1.5z
0.5y+1.5z=0.5x

x=y+3z