Correct. Find the mean for each data set:

Leaving at 5 p.m.: $\displaystyle\frac{{{45}+{50}+{48}+{52}+{55}}}{{5}}={50}\usepackage{cmbright}\Huge\$

Leaving at 6 p.m.: $\displaystyle\frac{{{36}+{42}+{38}+{34}+{40}}}{{5}}={38}\usepackage{cmbright}\Huge\$

The difference between these averages is $\displaystyle{50}-{38}={12}\usepackage{cmbright}\Huge\$ , or 12 minutes.