Adding till 20

Calculate:

The number of examples:
Numerical difficulty:
Range of values:
Multiplicity:

7	+	5	=
9	+	5	=
8	+	9	=
9	+	8	=
4	+	1	=
8	+	5	=
11	+	6	=
2	+	1	=
4	+	3	=
8	+	2	=