Subtract till 100

Calculate:

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

70	-	24	=
51	-	3	=
52	-	35	=
42	-	38	=
58	-	9	=
20	-	7	=
91	-	37	=
57	-	14	=
34	-	25	=
90	-	41	=