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

一、12 11 12
7 8 6
12 14 13
9 9 7
15 12 11
9 8 9
14 11 11
8 7 5
13 13 10
9 8 8

二、在$□$里填合适的数。
$□ + 5 = 12$ $2 + □ = 11$ $□ - 4 = 7$
$3 + □ = 11$ $13 - □ = 5$ $5 + □ = 11$
$12 - □ = 4$ $5 + □ = 14$ $□ - 6 = 6$

二、7 9 11
8 8 6
8 9 12