一、算一算。
$ 20 + 4 =
$ 4 + 20 =
$ 24 - 4 =
$ 24 - 20 =
$ 20 + 4 =
24
$$ 4 + 20 =
24
$$ 24 - 4 =
20
$$ 24 - 20 =
4
$答案
24
24
20
4
24
20
4
二、在括号里填上合适的数。
$ 72 - (
$ 30 + (
$ 3 + (
$ 40 + (
$ 76 - (
$ 80 + (
$ (
$ (
$ (
$ (
$ (
$ 37 - (
$ 72 - (
2
) = 70 $$ 30 + (
7
) = 37 $$ 3 + (
40
) = 43 $$ 40 + (
5
) = 45 $$ 76 - (
70
) = 6 $$ 80 + (
7
) = 87 $$ (
33
) - 3 = 30 $$ (
50
) + 9 = 59 $$ (
25
) - 20 = 5 $$ (
80
) + 4 = 84 $$ (
65
) - 5 = 60 $$ 37 - (
30
) = 7 $答案
2 7 40 5 70 7 33 50 25 80 65 30
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