Answer:
It's C.
Explanation:A squared plus b squared equals c squared, then square root the c value to get your answer
So A=18 and B=24 right? But C, the diagonal length of the table is unknown. If we split the table into two triangle instead of a rectangle, the diagonal length becomes a missing side. So now you can do 18^2 + 24^2 = C^2 or 324+576=900 square rooted. or 30.
Actually those do look correct which ones did you get wrong?
