Adding till 20

Calculate:

Number of examples:
Numerical difficulty:
Range of values:
Multiplicity:

6	+	3	=
4	+	3	=
2	+	4	=
6	+	4	=
9	+	4	=
3	+	3	=
10	+	6	=
2	+	3	=
7	+	11	=
7	+	2	=