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