Solve for x if log_3 2x - log_3 (x + 5) = 0.

$\log_3 2x - \log_3 (x + 5) = 0$

$\log_3 \dfrac{2x}{x + 5} = 0$

$\log_3 \dfrac{2x}{x + 5} = \log_3 1$
 

Hence,
$\dfrac{2x}{x + 5} = 1$

$2x = x + 5$

$x = 5$