答案解:①5x+28=71 5x+28-28=71-28 5x=43 5x÷5=43÷5 x=8.6②8.7-1.2x=3.9 8.7-1.2x+1.2x=3.9+1.2x 8.7=3.9+1.2x 3.9+1.2x-3.9=8.7-3.9 1.2x=4.8 1.2x÷1.2=4.8÷1.2 x=4 ③8x-2.6x=37.8 5.4x=37.85.4x÷5.4=37.8÷5.4 x=7④0.75x-0.95×4=8.5 0.75...