①15:x=7:28
②34:x=0.25:8
③x:15=30:18
④14:56=x:113
×4.2= 10.4﹣0.8= 44÷ = 0.11÷0.1=
÷ = 8.7÷29= × = 6×( ﹣ )=
+0.625= ×= 24÷40%= 7.2÷0.9÷0.8=