let the axis do the work. draw a pair of axis as you would in the Cartesian plane. let the positive y direction be north, the negative y direction be south, etc.

you want to draw a vertical line of length 4 with an arrow at the top of it, this is the first vector. from the terminal point of that vector, draw a line, 5 units in length going to the right such that it would make a 45 degree angle with the x-axis, draw an arrow at the end. these two are the displacement vectors. then draw a vector from the starting point of the first line to the terminal point of the last line. this is your net displacement vector