Answer
The friend's distance from the camera should be $~~540~cm$
Work Step by Step
We can use similar triangles to find the required distance $d$:
$\frac{d}{180~cm} = \frac{15~cm}{5.0~cm}$
$d = \frac{(15~cm)(180~cm)}{5.0~cm}$
$d = 540~cm$
The friend's distance from the camera should be $~~540~cm$
