To find the cost of the pizza \( c \) when it is split evenly among 4 people, and each person spent $5, we can set up the equation based on the information given.
Since the total cost \( c \) is divided by the 4 people, we have:
\[ \frac{c}{4} = 5 \]
This means each person spends $5, which is equal to the total cost divided by the number of people.
Thus, the correct equation to use is:
\(\frac{c}{4} = 5\)