Erbijsommen en erafsommen tot 20 oplossen
In de mix
1.
12
8
+
=
2.
17
12
–
=
3.
15
3
+
=
4.
14
13
–
=
5.
13
2
+
=
6.
12
1
+
=
7.
20
17
–
=
8.
17
13
–
=
9.
13
1
+
=
10.
19
16
–
=
11.
20
16
–
=
12.
18
14
–
=
13.
18
12
–
=
14.
15
3
+
=
15.
15
1
+
=
16.
15
12
–
=
17.
17
15
–
=
18.
18
16
–
=
19.
15
13
–
=
20.
12
1
+
=
21.
13
12
–
=
22.
13
6
+
=
23.
12
0
+
=
24.
13
12
–
=