(1)x÷0.8=2.5 x÷0.8×0.8=2.5×0.8 x=2 (2)9.53-x=6.28 9.53-x+x=6.28+x 6.28+x=9.53 6.28+x-6.28=9.53-6.28 x=3.25 (3)x+0.8=2.5 x+0.8-0.8=2.5-0.8 x=1.7 (4)25-5x=15 25-5x+5x=15+5x 25=15+5x 25-15=15+5x-15 10=5x 10÷5=5x÷5 x=2