302+303+304+305+306
=( )×( )
=( )
①36×()
②1.3×37.5%+2.7×
③ [()]
④13÷()×
①3.6﹣2.8+7.4﹣7.2
②1.25×1.6×25
③÷4
④÷[(﹣)×]