18X+2/3X*8=2870 70/3x=2870x=2870*3/70x=123x-（1/4x+7）-[2/5（x-1/4x-7）+2]=5/18xx-1/4x-7-2/5(x-1/4x-7)-2=5/18x3/5(3/4x-7)-2=5/18x9/20x-21/5-2=5/18x81/180x-50/180x=31/531/180x=31/5x=31/5*180/31x=36