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