Answer: 19.5cm
Step-by-step explanation:
Using pythagoream's theorem.
[tex]c^2=a^2+b^2[/tex]
in your case this would be;
[tex]z^2=x^2+y^2\\z=\sqrt{x^2+y^2}[/tex]
[tex]z=\sqrt{(7.5cm)^2+(18cm)^2}\\z=\sqrt{56.25cm^2+324cm^2}\\ z=\sqrt{380.25cm^2}\\ z=19.5cm[/tex]
