I having hard time figuring this out.

You are on a cruise ship traveling north at a speed of 15 m/s with respect to land.
3)Your friend is sitting on another cruise ship traveling south at 12 m/s. As you walk toward the back of your ship at 1.8 m/s, what is your velocity with respect to your friend?

You only need to think about those for a while. The ship you're on is going North at 14 m/s, you walk towards the South at 1.8 m/s.

How fast are you going north, relative to the ground? Would you be going faster or slower in the north direction relative to the land?

Same thing next. Your friend is going at 12 m/s south, while you are going north. You you see each other coming faster towards each other, or slower?

You see the same thing when you're in a car and observe other cars passing by, either in the same direction or in the opposite direction.

What do you get? :)