40+(x-20)乘0.2=30+(x-200)乘0.340+0.2x-4=30+0.3x-600.3x-0.2x=40-4-30+600.1x=66x=66÷0.1x=660
40+(x-20)乘0.2=30+(x-200)乘0.340+0.2x-4=30+0.3x-600.2x-0.3x=30-60-40-4-0.1x=-74x=-74/(-0.1)x=740