Adding till 100

Calculate:

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

7	+	15	=
72	+	28	=
9	+	13	=
28	+	42	=
45	+	53	=
45	+	20	=
5	+	5	=
45	+	22	=
25	+	21	=
52	+	42	=