a) You will need vector addition, which is just adding vectors componentwise.

b) Use the law of cosines

c) Use the formula where is the cross-product and is the magnitude.

d) Use the formula where is the dot-product.

If you don't understand those terms you will need to look them up. I believe your instructor intends for you to learn this on your own, so I won't be able to help you any further without an attempt at a solution.