Calculus
posted by Wendy .
What is the horizontal asymptote of :
y=23x/x+18
k so i know that the horizontal asymptote is 18 so that the denominator will equal zero.

I assume you mean:
y = 23 x / (x+18)
indeed the denominator goes to zero at x = 18 so you get undefined vertical asymptote at x = 18
as x gets very large positive, this looks like 23 x/x > 23
as x gets very large negative it looks like
23 (x/x) > 23