One approach to part (a) uses the scalar product; another would be to think in terms of slopes.

One approach to (b) is to find a unit direction vector, and then make it the right length.

One approach to (c) is to write parametric equations for position, and eliminate t.

But for all of this, we'll want to help you with the methods you have learned, which is why we need to see either your work, or what you know that is relevant.