400÷80= 7.7+2.3= 4.2÷0.6= 1﹣0.91=
0.04×1000= 10÷1.25×9= 24×0.25= 23﹣1=
+= ×20=
①2021÷1.25÷
②5.74×12.5%+1.26÷8+
③(-0.6)÷(-)
④0.8÷[(+)×]