First to note is how average speed, v, distance, d, and time, t, are related. This is given by v = d/t. The journey is split into two parts, but we are only asked for the total distance and average speed. It is clear that the total distance is given by 10m + 10m = 20m, from the first and second parts of the journey. The total time is t = 5s + 10s = 15 s. Hence v = 20/15 = 1.33 m/s. The total displacement can be determined by drawing a triangle of the path travelled. Using Pythagoras Theorem one can determine that the displacement, D, is D = the square root of(10^2+10^2 = 200)= 14.1 m north-east. The velocity, V, is then given by V = D/t, similar to how distance and speed are related. So V = 14.1/15 = 0.94 m/s north-east. Importantly the direction are required for displacement and velocity as they are vectors.