Stuck on vector addition and subtraction

[victorhugo]

Hello, here is a couple of example problems I'm not sure how to do, if someone could please explain how to do it I would greatly appreciate it!

Subtraction:
"A river flows at 0.8 m/s. If a boat moves across the water at 2m/s at what angle should it point so that it moves straight across the river perpendicular to the bank?"

Addition:
"A plane flies at a bearing of 270 degrees at 200km/h through a cross wind blowing from a bearing of 360 degrees at 80km/h. What is the plane's velocity over the ground?"

Thank you!

 

[tms]

You have to at least make an attempt to answer the questions.

 

[victorhugo]

I actually don't know what to do... the only way I learned is to get the displacement by using Pythagoras theorem, then diving that by the time to get the average velocity, so that's why I'm asking if someone could tell me what to do here :/

 

[tms]

Take one of your problems, and use the procedure you know on it. Show your work. Then people here can help you.