$10 + 5 =$ $3 + 10 =$ $6 + 10 =$ $10 + 8 =$ $10 + 10 =$
$15 - 5 =$ $13 - 3 =$ $16 - 6 =$ $18 - 10 =$ $20 - 10 =$
$15 - 10 =$ $13 - 10 =$ $16 - 10 =$ $18 - 8 =$ $20 - 20 =$

$10 + 5 = 15$
$3 + 10 = 13$
$6 + 10 = 16$
$10 + 8 = 18$
$10 + 10 = 20$
$15 - 5 = 10$
$13 - 3 = 10$
$16 - 6 = 10$
$18 - 10 = 8$
$20 - 10 = 10$
$15 - 10 = 5$
$13 - 10 = 3$
$16 - 10 = 6$
$18 - 8 = 10$
$20 - 20 = 0$

$13 + 2 =$ $19 - 8 =$ $14 + 3 =$ $3 + 16 =$ $17 - 2 + 4 =$
$17 - 3 =$ $15 - 4 =$ $6 + 12 =$ $11 + 7 =$ $14 + 4 - 6 =$
$18 - 5 =$ $16 - 2 =$ $15 - 1 =$ $12 + 4 =$ $17 - 6 - 1 =$
$3 + 14 =$ $19 - 7 =$ $17 - 7 =$ $18 + 1 =$ $15 + 3 - 4 =$

13+2=15
19-8=11
14+3=17
3+16=19
17-2+4=19
17-3=14
15-4=11
6+12=18
11+7=18
14+4-6=12
18-5=13
16-2=14
15-1=14
12+4=16
17-6-1=10
3+14=17
19-7=12
17-7=10
18+1=19
15+3-4=14

1. 比大小。
$18$◯$17$ $12$◯$11$ $17$◯$9$ $16$◯$19$ $13$◯$20$
$16 - 3$◯$13 - 1$ $18 - 3$◯$18 - 4$ $19 - 9$◯$16 + 3$

1. $18＞17$
2. $12＞11$
3. $17＞9$
4. $16＜19$
5. $13＜20$
6. $16 - 3=13$，$13 - 1 = 12$，$13＞12$，所以$16 - 3＞13 - 1$
7. $18 - 3=15$，$18 - 4 = 14$，$15＞14$，所以$18 - 3＞18 - 4$
8. $19 - 9=10$，$16 + 3=19$，$10＜19$，所以$19 - 9＜16 + 3$

2. 填一填。
$7 + ◻ = 19$ $5 + ◻ = 17$ $3 + ◻ = 15 - 2$
$◻ - 3 = 13$ $19 - ◻ = 9$ $12 - ◻ = 13 - 3$
$◻ + 6 = 16$ $◻ + 2 = 14$ $11 + ◻ - 5 = 10$

12,12,10,16,10,2,10,12,4

$7 + ◻ = 19$，$19-7=12$，故填12；
$5 + ◻ = 17$，$17-5=12$，故填12；
$3 + ◻ = 15 - 2$，$15-2=13$，$13-3=10$，故填10；
$◻ - 3 = 13$，$13+3=16$，故填16；
$19 - ◻ = 9$，$19-9=10$，故填10；
$12 - ◻ = 13 - 3$，$13-3=10$，$12-10=2$，故填2；
$◻ + 6 = 16$，$16-6=10$，故填10；
$◻ + 2 = 14$，$14-2=12$，故填12；
$11 + ◻ - 5 = 10$，$11-5=6$，$10-6=4$，故填4。