一、在$□$里填合适的数。

一、8 + 7 = 15

7 + 6 = 13

7 + 7 = 14

二、口算。
$8 + 2 + 3 =$
$8 + 2 + 1 =$
$8 + 2 + 5 =$
$8 + 5 =$
$8 + 3 =$
$8 + 7 =$
$8 + 2 + 4 =$
$8 + 2 + 7 =$
$8 + 2 + 2 =$
$8 + 6 =$
$8 + 9 =$
$8 + 4 =$
$7 + 3 + 5 =$
$7 + 3 + 3 =$
$7 + 3 + 7 =$
$7 + 8 =$
$7 + 6 =$
$7 + 10 =$
$7 + 3 + 4 =$
$7 + 3 + 2 =$
$7 + 3 + 6 =$
$7 + 7 =$
$7 + 5 =$
$7 + 9 =$
$3 + 5 + 6 =$
$4 + 6 + 7 =$
$2 + 6 + 9 =$
$4 + 3 + 5 =$
$5 + 3 + 8 =$
$4 + 4 + 4 =$

二、13 11 15
13 11 15
14 17 12
14 17 12
15 13 17
15 13 17
14 12 16
14 12 16
14 17 17
12 16 12