Physics reflections problem- help! due in 3 hours!?

Suppose that you want to take a photograph of yourself as you look at your image in a flat mirror 2.9 m away. For what distance should the camera lens be focused?

Twice the distance to the mirror.

1/o + 1/i = 1/f

For a flat mirror, the radius of curvature and the focal length are infinite, so 1/f is zero, so the image is behind the mirror at the same distance the object is in front.