Question

How do you do this? It's so confusing! Please help!

Answer 1

Check the picture below.

notice AB ⟂ BC , whilst ∡B = 30°.

now, if we run a perpendicular line from C to AB, it'll be a 90° angle at M, however ∡AMC has to be 105°, so it has to be slanted more towards A, like in the picture, and surely you already know which one is the shortest.