①25%x=75 0.25x÷0.25=75÷0.25 x=300 ②x+30%x=390 1.3x=390 1.3x÷1.3=390÷1.3 x=300 ③80%x-60%x=28 0.2x÷0.2=28÷0.2 x=140
