Please help, this question is really hard :(
AOD = 180 - BOC
AOD = 3.5 BOC or BOC = AOD/3.5 sub in to top equation
AOD = 180 - AOD/3.5
AOD = 140 DEGREES
I really like your solution, but I don't think AOD = 180 - BOC.
Instead, I think we need to start with the fact that AOC = 90 and COA = 90 since lines are perpendicular.