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