algebra
posted by JO on .
Use your calculator to evaluate the following expression if x = –2.57, y = 1.55, and z = –1.98. Round your answer to the nearest tenth.

Since you already told us what x, y and z are, what is there to evaluate?
You seem to have left out what you call the "following expression", which is a probably formula of some kind that involves x, y and z.