Adding till 20

Calculate:

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

2	+	8	=
7	+	8	=
5	+	8	=
8	+	7	=
6	+	8	=
6	+	6	=
3	+	2	=
9	+	10	=
3	+	3	=
2	+	5	=