1. The problem statement, all variables and given/known data

A delivery man travels 35 mi northwest to his first stop, 60 mi in a direction 35° west of south to his second stop. His third stop is supposed to be 100 mi west of his original position. What must his third displacement be (magnitude and direction) for him to reach his destination?

2. Relevant equations

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3. The attempt at a solution

I drew this inaccurate graph.

I'd rather not make an accurate graph for these kind of problems since I don't always have the resources to do so. I'm familiar with SOHCAHTOA, but I'm not sure how to use it to find the solution to this problem.

This is what someone suggested for a similar problem, but I'm having trouble understanding it.

Let the starting point be O. the firsat stop be A, second stop be B and third stop be C.
In triangle OAC, OA, OC and angle AOC is given.Using cosine rule you can find AC, and usind sine rule you can find angle OAC. Repeat the same thing for the triangle CAB.