Answer:

Step-by-step explanation:
Given


Required
Find g(3)
Since g(x) is a linear function, then:

For: 





For: 




Substitute 



So, the function is:


Calculate g(3)



Because the angels are equivalent, you can set the expressions equal to each other and solve. You will find that x = 54.
Work shown in image - let me know if I made any errors or if you have any additional questions.
They are also perpendicular to the top line of the roof