14:35=14/35 2:12.5=4:25 3/5:2/7=21:10
=2/5 =4/25
40:125=8:25(前项和后项同时除以8)
18:1.8=10:1(前项和后项同时除以1.8)
2/5:1/4=8:5(前项和后项同时乘20)