一、口算。
$17 - 9 =$ $12 - 8 =$ $9 + 6 - 7 =$
$7 + 5 =$ $6 + 8 =$ $13 - 6 - 5 =$
$14 - 5 =$ $16 - 5 =$ $9 + 5 - 4 =$
$5 + 8 =$ $7 + 7 =$ $12 - 7 + 6 =$
$11 - 7 =$ $18 - 10 =$ $8 + 6 - 5 =$
$9 + 7 =$ $4 + 7 =$ $13 - 4 - 4 =$
$13 - 8 =$ $11 - 2 =$ $15 - 7 + 8 =$
$6 + 5 =$ $15 - 3 =$ $16 - 9 + 5 =$
$16 - 7 =$ $8 + 7 =$ $5 + 7 - 3 =$
$4 + 8 =$ $15 - 6 =$ $13 - 7 + 6 =$

一、8 4 8
12 14 2
9 11 10
13 14 11
4 8 9
16 11 5
5 9 16
11 12 12
9 15 9
12 9 12

二、在$□$里填合适的数。
$5 + □ = 11$ $□ - 4 = 8$ $12 - □ = 9$
$□ - 6 = 6$ $9 + □ = 17$ $□ + 6 = 13$
$13 - □ = 7$ $□ + 4 = 12$ $□ - 7 = 5$

二、6 12 3
12 8 7
6 8 12