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