Subtract till 100

Calculate:

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

69	-	48	=
49	-	46	=
48	-	36	=
84	-	40	=
58	-	10	=
35	-	32	=
45	-	37	=
80	-	42	=
81	-	30	=
79	-	31	=