Please see the attached file.
All the three vectors in the problem are as shown in the following figure.
Let be the resultant vector.
You can solve the problem in two ways.
Resolve and into their perpendicular components along X and Y axes. Perform the addition or subtractions of these perpendicular components as follows.
I think you know how to resolve a vector.
See for example, resolving vector A into its components along X & Y axes.
The X-component of vector A is denoted by Ax and
Y-component by Ay.
These components are
Ax = A cos 600 along +ve direction of X-axis.
Ay = A sin 600 along +ve direction of X-axis.
Similarly resolve vector B into its ...
Solution takes a diagram of 3 displacement vectors and shows how to find their resultant. Attached as a .doc file.