The number of outcomes in the sample space equals the number of snack pieces:

$\displaystyle{5}+{4}+{5}+{1}={15}\usepackage{cmbright}\Huge\$

The number of outcomes for the event of pulling a pretzel from the bag is 5. So $\displaystyle\frac{{5}}{{15}}\usepackage{cmbright}\Huge\$ , or $\displaystyle\frac{{1}}{{3}}\usepackage{cmbright}\Huge\$ , is the probability of pulling a pretzel from the bag.