Subtract till 100

Calculate:

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

65	-	37	=
90	-	48	=
81	-	6	=
91	-	44	=
94	-	9	=
53	-	26	=
65	-	12	=
43	-	42	=
33	-	7	=
35	-	22	=