一、口算。
$9 + 7 =$
$9 + 8 =$
$9 + 0 + 9 =$
$9 + 1 =$
$1 + 9 =$
$9 + 3 - 2 =$
$9 + 6 =$
$9 + 9 =$
$8 + 1 + 3 =$
$19 - 9 =$
$10 + 9 =$
$9 + 7 - 5 =$
$9 + 5 =$
$19 - 6 =$
$9 + 9 - 10 =$
$9 + 3 =$
$14 + 5 =$
$3 + 6 + 9 =$
$10 - 9 =$
$5 + 4 =$
$7 + 2 + 6 =$
$9 + 4 =$
$9 + 2 =$
$9 + 4 - 1 =$
$2 + 17 =$
$16 - 3 =$
$2 + 7 + 8 =$
$9 + 10 =$
$0 + 9 =$
$6 + 3 + 7 =$

一、16 17 18
10 10 10
15 18 12
10 19 11
14 13 8
12 19 18
1 9 15
13 11 12
19 13 17
19 9 16

二、在$□$里填合适的数。
$□ + 9 = 11$
$9 + □ = 13$
$9 + □ = 17 - 2$
$9 + □ = 12$
$9 + □ = 14$
$□ + 9 = 15 + 1$
$□ + 9 = 18$
$□ + 9 = 19$
$□ + 9 = 10 - 1$

二、2 4 6
3 5 7
9 10 0