一、口算。
$9 + □ = 14$
$9 + □ = 18$
$17 - 9 = 10 - 9 + □$
$14 - 9 =$
$18 - 9 =$
$11 - 9 = 10 - 9 + □$
$9 + □ = 16$
$9 + □ = 17$
$13 - 9 = 10 - 9 + □$
$16 - 9 =$
$17 - 9 =$
$14 - 9 = 10 - □ + □$
$9 + □ = 15$
$9 + □ = 10$
$12 - 9 = 10 - □ + □$
$15 - 9 =$
$10 - 9 =$
$15 - 9 = 10 - □ + □$
$9 + □ = 12$
$9 + □ = 11$
$13 - 9 = 13 - 3 - □$
$12 - 9 =$
$11 - 9 =$
$15 - 9 = 15 - 5 - □$
$9 + □ = 19$
$9 + □ = 13$
$16 - 9 = 16 - □ - □$
$19 - 9 =$
$13 - 9 =$
$17 - 9 = 17 - □ - □$

一、5 9 7
5 9 1
7 8 3
7 8 9 4
6 1 9 2
6 1 9 5
3 2 6
3 2 4
10 4 6 3
10 4 7 2

二、连一连。

二、×××