Thank you, that was very good. Though, for part c), since you'd already figured out that alpha = 80 degrees, you could have bypassed using the cosine rule, and recognised that the internal angles of a triangle = 180 degrees. From there, we have 180 - 80 - 70 = 30 degrees. That said, I really appreciated your instruction, I was never taught true bearings and found it a bit confusing, so thank you for clearing that up for me.
8 months late but if you have a right triangle you use trigonometry to find the missing side if you are given theta. But I don't think you can solve a 1 side and 1 angle non right triangle