Erbijsommen en erafsommen tot 20 oplossen
In de mix
1.
11
1
+
=
2.
12
8
+
=
3.
13
7
+
=
4.
15
13
–
=
5.
19
1
+
=
6.
20
17
–
=
7.
18
17
–
=
8.
15
5
+
=
9.
18
16
–
=
10.
13
1
+
=
11.
18
16
–
=
12.
15
13
–
=
13.
15
12
–
=
14.
13
12
–
=
15.
17
14
–
=
16.
16
2
+
=
17.
13
1
+
=
18.
12
3
+
=
19.
12
8
+
=
20.
18
12
–
=
21.
18
1
+
=
22.
20
16
–
=
23.
15
12
–
=
24.
12
2
+
=