Subtract till 400

Calculate:

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

312	-	142	=
243	-	93	=
310	-	69	=
287	-	16	=
240	-	190	=
71	-	46	=
340	-	73	=
340	-	109	=
121	-	121	=
247	-	134	=