I need help I have no clue on what to do

Answer:
30 units
Step-by-step explanation:
Given is a right angled triangle and c represents hypotenuse.
Therefore, by Pythagoras theorem:
[tex]c = \sqrt{ {18}^{2} + {24}^{2} } \\ = \sqrt{324 + 576} \\ = \sqrt{900} \\ c= 30 \\ [/tex]