well, if I am reading this right it just wants to know how to get from one point to another... so think of M as 1/2 of b and N as 1/2 of a.
so a) (i) you just take the direction of b to get from b to c
(ii) to get from a to c, you need to go over to B (a) and up to C (b) so it would be a+c
b) (i) same as a) (i) just the other direction.
(ii) N to D is just 1/2 of a so
[tex] \frac{1}{2} a[/tex]
c) use what you just learned to do c!
hope this helps!
