How to count number of element occurrences in a list in Prolog

Question

i m new in prolog that s why may be the question is easy for you but i couldnt find the answer. Can someone please help me.

I just want

a count function s.t

Answer 1

co(X,L) :- co(X,[],L).

co([],A,A).
co([X|Xs], A, L) :- p(X-Z,A,R), !, Z1 is Z+1, co(Xs, [X-Z1|R], L). 
co([X|Xs], A, L) :- co(Xs, [X-1|A], L). 

p(X-Y,[X-Y|R],R):- !.
p(X,[H|Y], [H|Z]) :- p(X,Y,Z).

I did not use very meaningful names on purpose. Try to understand what each one of the predicates does.