一、口算。
$15 - 7 =$
$12 - 9 =$
$14 - 8 + 3 =$
$16 - 7 =$
$14 - 7 =$
$17 - 8 - 4 =$
$17 - 8 =$
$11 - 7 =$
$12 + 2 - 7 =$
$10 - 8 =$
$15 - 9 =$
$3 + 10 - 8 =$
$18 - 8 =$
$12 - 7 =$
$7 + 9 - 8 =$
$10 - 7 =$
$11 - 9 =$
$12 - 7 + 2 =$
$16 - 8 =$
$12 - 8 =$
$7 + 5 - 8 =$
$11 - 8 =$
$14 - 9 =$
$11 - 8 - 1 =$
$13 - 7 =$
$15 - 8 =$
$16 - 3 - 8 =$
$18 - 9 =$
$17 - 7 =$
$15 - 7 + 6 =$

一、8 3 9
9 7 5
9 4 7
2 6 5
10 5 8
3 2 7
8 4 4
3 5 2
6 7 5
9 10 14

二、连一连。

二、