To solve this problem, first, let's find the speed of the father.
Let x be the speed of the father.
The speed is distance/time.
Then,
![Speed=(36)/(12)=3\text{ }(miles)/(hours)](https://img.qammunity.org/2023/formulas/mathematics/college/hcdpn5q85k9rqifivlkcfvgbc93jcpof5x.png)
Second, let's find the speed of the soon.
Let y represent the speed of the soon.
Since the speed is twice the speed of the father:
y = 2x:
![\begin{gathered} y=2*3 \\ y=6\text{ }(miles)/(hour) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/v32jzu4d4ios9tqvbpp6q7x4w96aud6o4r.png)
Finally, find the distance traveled in 9 hours.
The distance is the product of the time and the speed:
![\begin{gathered} distance=9*6 \\ distance=54\text{ }miles \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4h5tq3zuhhf0k34c70s8a128fy60gdt7pp.png)
Answer: 54 miles.