Hey guys i saw this questin in my notes and i dont remember/understand how the answer was found. Please see attached pdf

 

You have your terms reversed on the right side of your current equation:
(9 cos (5t) - 6) / 3 = (6 - Vout) / 4

 

Legend! Thanks very much for pointing out that blunder. Wow but the way i did that is so much simpler than the way that the teacher did it. I was worried that there was something conceptually wrong with the way i was doing it.

Cheers