A level p3 maths

So i am stuck on 9709/32/M/J/19 question no.9. I do not understand the concept of vector at all. i just don't get anything from the question itself. Someone please help me with this question and also vector. Pleaseee!!!! CIE is near.

I presume you mean this one (it helps to post the question, your attempt, the ms, ...)
https://www.youtube.com/watch?v=50RojiVt4ho
So a line can be described by
r = p + mu*d
where p is a point on the line (vector) and d is the direction vector and mu a scalar which represents how far along on the direction vector you are from the point p. So for the first part, represent the (extended) line AB in a similar format and show there is no values for mu (and lambda say) which means the lines intersect (so the 3 equations for x,y,z in the two variables mu,lambda are inconsistent).