This question is a Master-level, three-segment motion. There are two northward movements and one southward movement. When it comes to the direction-ignorant distance quantity, these directions do not matter. Simply add up the length of the three movements and you have calculated the amount of ground that is covered.
The quantity displacement is a direction-conscious quantity. Direction matters! Both northward movements takes the hockey puck away from the starting position; they add together to give the hockey puck a northward displacement. But the southward movement partially negates this motion and takes the hockey puck back towards the starting point (but not past it). Because the second movement is in the opposite direction as the other two movements, one must subtract this from the length of the two northward segments.
A common approach for questions like these involves defining North as the positive direction and South as the negative direction. A 16-meter southward movement is thought of as a -16 m displacement. The overall displacement is the sum of two positive (North) and one negative (South) movements. If the sum turns out to be negative, then the direction is opposite of North; that is, it would be South.
Finally, this 3-segment "Master"-level question ( like the 4-segment "Wizard" level questions) is more difficult. As such, it becomes useful to learn to diagram the situation. Draw an arrow for each segment of the motion; and draw the arrow in the described direction and approximately the relative length. Where one arrow ends, the next arrow begins. The process of diagramming helps a learner to visualize displacement as the overall change in position relative to the starting position.