Answer: [tex]8\ hours[/tex]
Step-by-step explanation:
You know that Mr. Wilson uses the following equation to find the cost:
[tex]D= 3H+6[/tex]
Then, if Mr. Wilson spent $30, you can follow these steps in order to calculate how many hours he parked in the parking garage:
1. You need to substitute [tex]D=30[/tex] into the given equation:
[tex]30= 3H+6[/tex]
2. Now, you must solve for "H":
[tex]30= 3H+6\\\\30-6=3H\\\\24=3H\\\\\frac{24}{3}=H\\\\H=8[/tex]
Therefore, based on the result, you can conclude that Mr. Wilson parked his car in the parking garage for 8 hours.