$$\\-5+-\frac{1}{3}\\\\
=-5-\frac{1}{3}\\\\
$Now on a number line you would start at -5 and then you would go $\\ \frac{1}{3} $ to the negative (left) side.$\\
$That means you would go further away from 0 - it would become more negative$\\\\
=-5\frac{1}{3}\\\\\\
$This is really the same as $ -(5+\frac{1}{3})$$