23×3= 680-450= 72÷9= 240+360=
+= -= 467×0= 48+27=
500×7= 798-201≈ 81×4≈ 298+701≈
①﹣(+)
②8.89﹣1.84﹣3.16
③÷9+×
④12.5×0.32×2.5