二、在$□$里填合适的数。
$15 - 5 - □ = 4$
$9 - 6 - □ = 2$
$□ + 2 + 6 = 16$
$7 - 4 + □ = 13$
$12 - 2 + □ = 16$
$6 + 4 + □ = 19$
$14 + 2 - □ = 6$
$10 - 9 - □ = 0$
$12 - 2 + □ = 15$
$9 + 10 - □ = 10$
$5 + 12 - □ = 16$
$14 + □ - 10 = 4$
$□ + 6 - 9 = 1$
$7 - 5 + □ = 10$
$15 - □ - 8 = 2$
$9 - □ - 4 = 1$
$9 + 10 - □ = 14$
$12 + 7 - □ = 10$
$3 + 11 - □ = 10$
$□ + 5 - 10 = 6$
$7 - 2 - □ = 5$
$15 + 3 - □ = 10$
$8 - 6 - □ = 0$
$13 - 3 + □ = 14$
$□ + 3 + 5 = 15$
$□ + 11 + 2 = 19$
$15 - □ - 7 = 3$
$9 - 2 + □ = 10$
$5 + 14 - □ = 11$
$□ + 1 + 10 = 15$

1.6
2.1
3.8
4.10
5.6
6.9
7.10
8.1
9.5
10.9
11.1
12.0
13.4
14.8
15.5
16.4
17.5
18.9
19.4
20.11
21.0
22.8
23.2
24.4
25.7
26.6
27.5
28.3
29.8
30.4

三、在○里填“+”或“-”。
19○9○2=8
16○6○5=15
12○7○5=14
15○3○6=12
8○5○14=17
9○5○6=10
7○3○2=12
4○6○6=16
9○1○8=18
9○1○2=10
18○5○6=19
3○4○3=10
8○6○8=10
4○4○8=0
17○7○10=0

1.- -
2.- +
3.+ -
4.+ -
5.- +
6.- +
7.+ +
8.+ +
9.+ +
10.- +
11.- +
12.+ +
13.- +
14.+ -
15.- -