(56-4x)/2=(1-0.4)x+8.428-2x=0.6x+8.428-8.4=2x+0.6x2.6x=19.626x=19613x=98x=98/13
（56-4X）÷2=（1-0.4）X+8.428-2X=0.6X+8.42X+0.6X=28-8.42.6X=19.6X≈7.54
