(1.8-8x)/1.2-(1.3-3x)/2-(5x-0.4)/0.3=0（18-80x）/12-(1.3-3x)/2-(50x-4）/3=0（18-80x）-6(1.3-3x)-4(50x-4）=018-80x-7.8+18x-200x+16=0-80x+18x-200x=0-18+7.8-16-262x=-26.2x=0.1