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