一、口算。
15 - 5 = 92 - 2 = 11 - 2 + 50 =
28 - 8 = 70 - 50 = 85 - 80 + 5 =
5 + 6 = 4 + 80 = 4 + 60 - 4 =
14 - 7 = 77 - 7 = 16 - 9 + 5 =
17 - 9 = 6 + 70 = 19 - 3 - 8 =
3 + 8 = 25 - 5 = 3 + 4 + 80 =
12 - 3 = 46 - 40 = 14 - 7 + 40 =
7 + 5 = 10 + 40 = 28 - 8 + 30 =
9 + 6 = 40 + 8 = 41 - 40 + 9 =
74 - 70 = 30 + 40 = 64 - 60 + 9 =

一、10 90 59
20 20 10
11 84 60
7 70 12
8 76 8
11 20 87
9 6 47
12 50 50
15 48 10
4 70 13

二、在$□$里填合适的数。
$□$ + 20 = 60 33 - $□$ = 30 10 + $□$ = 19
26 - $□$ = 6 $□$ + 60 = 67 80 - $□$ = 50
$□$ + 7 = 57 77 - $□$ = 70 50 + $□$ = 52

二、40 3 9
20 7 30
50 7 2