When an object is placed 8 millimeters from a concave spherical
mirror, a clear image can be projected on a screen 16 millimeters in
front of the mirror. If the object has a height of 4 millimeters, the
height of the image is?

Hi wyzgowski7-ga, and thanks for your question.

First, here's a good tutorial on lenses and mirrors:
://www.google.com/url?sa=U&start=2&q=http://www.rowan.edu/colleges/las/physicsandastronomy/LabManual/labs/LensesAndMirrors.pdf&e=9707

On the first page of this document, we have the equation for magnification:

m = i / p,

where m is the magnification, i is the image distance, and p is the
object distance.  From this, we have

m = i / p = 16mm / 8mm = 2

2 x 4mm = 8mm, so the height of the image is 8mm.

Please feel free to request clarification.

             -welte-ga