1. The problem states that Alexandra paid 7 dollars to park for 3 hours, and the parking garage charges a constant hourly rate. 2. We need to find an equation relating $p$, the number of hours parked, and $c$, the cost in dollars. 3. Since the rate is constant, the cost $c$ is directly proportional to the number of hours $p$. 4. The general formula for this relationship is $$c = r \times p$$ where $r$ is the hourly rate. 5. To find $r$, use the given values: $7 = r \times 3$. 6. Solve for $r$: $$r = \frac{7}{3}$$. 7. Substitute $r$ back into the formula: $$c = \frac{7}{3} p$$. 8. This equation shows the cost $c$ in dollars for $p$ hours parked at the constant hourly rate of $\frac{7}{3}$ dollars per hour. Final equation: $$c = \frac{7}{3} p$$