Hi, is this categorized as number theory?....the only text book my college libary has for this kind of stuff is like, 30 years old and not the easiest read!

This is an example in my workbook...if someone could spare the time to go through it that would be awesome.

Any help much appreciated!

Given thata = 2i + 3j − 4k, b = i − 2j and c = 5i + j + k. Find:

(a) the vector a + b − c

(b) the magnitude of a + b − c

(c) a unit vector parallel to a + b −