The answer is 370 miles west.
The ship goes 600 miles north, but he will later turn sought for 450 miles and later for another 150 miles:
600 miles north
450 + 150 = 600 miles east
So, it goes the equal distance north and south and these will not be taken into consideration.
No, let's see how far west it goes. First it travels 200 miles and later it travels another 170 miles:
200 + 170 = 370 miles