A camera has a convex lens of focal length 5 cm.

Step 1. The image. $\dfrac{1}{v} = \dfrac{1}{5\ \text{cm}} - \dfrac{1}{300\ \text{cm}} = \dfrac{60 - 1}{300\ \text{cm}} = \dfrac{59}{300\ \text{cm}}$, so $v = 5.08\ \text{cm}$.

Step 2. The magnification. $m = \dfrac{v}{u} = \dfrac{5.08\ \text{cm}}{-300\ \text{cm}} = -0.0169$.