To find out how much each person paid when splitting the dinner cost evenly, you can divide the total amount by the number of people.
The total dinner cost is $91.20 and there are 5 people (you and 4 friends).
\[ \text{Amount each person pays} = \frac{\text{Total cost}}{\text{Number of people}} = \frac{91.20}{5} = 18.24 \]
So, each person paid $18.24.