①400×5=2000, ②7×30=210, ③28÷7=4, ④40÷5=8, ⑤53+7=60, ⑥1-
5
6 =
1
6 ,⑦
2
5 +
3
5 =1,⑧
8
10 -
10 =
10 ,⑨
4 +
4 =1.