subtract vs cut back

subtract and cut back both are verbs.

Word	Noun	Adjective	Verb	Adverb
subtract	No	No	Yes	No
cut back	No	No	Yes	No

As verbs, cut back is a hypernym of subtract; that is, cut back is a word with a broader meaning than subtract:

Other hypernyms of subtract include bring down, cut, cut down, reduce, trim, trim back, trim down.

subtract (verb)	cut back (verb)
take off or away	place restrictions on
make a subtraction	cut down on; make a reduction in
	cultivate, tend, and cut back the growth of
	return in time