A ship sails from P to Q, then to R. The bearing of Q from P is 035°. The bearing of R from Q is 105°. Calculate 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 $035^\circ$, which means the angle between the North line at P and the line segment PQ is $35^\circ$.
By alternate interior angles, the angle between the line segment PQ and the South line at Q is also $35^\circ$.
The bearing of R from Q is $105^\circ$, which is the angle measured clockwise from the North line at Q to the line segment QR.
The angle from the North line at Q to the South line at Q is $180^\circ$.
Therefore,