参考：0%x+0.5x=1/4x+8/5x=多少30%x+0.5x=0.3x+0.5x=0.8x①1/5(x-8)+1/4x+x-1/7=6-23-x/5 ②3(0.7x+0.1)+2(0.25x-0.2)=5.1 ③(1.2+x)/0.4-(0.5x+1)/0.7=1①1/5(x-8)+1/4x+x-1/7=6-23-x/5 28﹙x－8﹚＋35x＋20﹙x－1...