If you draw the problem, it would look like that shown in the attached picture. The total length the ship will now travel can be solved using the Pythagorean theorem. The solution is as follows:
d = √(120)²+(100)²
d = 156.2 km
So, the ship will have to travel 156.2 km to the northwest direction.
d = √(120)²+(100)²
d = 156.2 km
So, the ship will have to travel 156.2 km to the northwest direction.