Three grades of milk are 1%, 2% and 3% milk fat by volume if x gallons of the 1% grade, Y gallons of the 2% grade Z gallons of the 3% are mixed x+y+z is 1.5% milk fat. What is x in terms of y and Z.

A) y+3Z
b)(Y+Z)/4
C)2Y+3Z
D)3Y+Z
E)3Y+4.5Z

I need a speedy approach