Answer:
5 m
Step-by-step explanation:
Displacement is the straight-line distance from the starting point to the end point. Student ends up 4m north and 3m west from where he started. Use pythagorean theorem to solve for displacement (d). 
d² = 3² + 4² = 25
d = 
 = 5 m
 = 5 m
Or, if you remember from geometry, a right triangle with legs of 3 and 4 has a hypotenuse of 5 (3-4-5 right triangle)