Find functions f and g such that f (g) = H if H (x) = 1/(x + 1).
don't/didn't do things that way in the UK). As far as I recall we learned
stuff as it was needed.
Some knowledge of composite functions is needed for the chain rule, but
as far as I recall a formal treatment of composite functions was not needed
in the courses I pursued until the transition to university real analysis (1st
year undergrad maths here).
Maybe one of our US helpers will be able to answer your question better.