A ship sails from P to Q on a bearing of 035°. It then sails from Q to R on a bearing of 105°. Find the interior angle ∠PQR.

Here's how to solve this navigation problem:

Step 1: Determine the interior angle $\angle PQR$.
The North line at P is parallel to the North line at Q.
The bearing of Q from P is $035^\circ$, so the angle between the North line at P and PQ is $35^\circ$.
By alternate interior angles, the angle between the line QP and the South line at Q is $35^\circ$.
The bearing of R from Q is $105^\circ$, which is the angle from the North line at Q (pointing North) clockwise to QR.
The angle between the North line at Q (pointing North) and the South line at Q is