5//6*(4.2x-1 1//5y)-5.4*(2//9-1.5y)=(5//6)*(4.2x-(6//5)*y)-5.4*((2//9)-1.5y)=(5//6)*(4.2x-1.2y)-5.4*((2//9)-1.5y)=3.5x-y-5.4*((2//9)-1.5y)=3.5x-y-(1.2-8.1y)=3.5x-y-1.2+8.1y=3.5x+7.1y-1.2
