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