Question

he number of cups in a 18.4 cm high stack is:

Answer 1

thanks for the information. Whats the question you are trying to ask?

Answer 2

You'll need to share the height of each cup.

Otherwise, use h to represent this height, in which case the answer would be 
18.4 cm / h(cm/cup).  "cm" will cancel here, so that  you'll be left with

18.4
------ cups (answer)
   h