<h2>Direction is represented by +9, indicating that is moving in a positive direction (upwards).</h2><h2>Zero is the reference point.</h2>
Step-by-step explanation:
So, basically, we need to apply a reference system to express directions, because all movements are represented respect to a reference point. In this case, number zero represents that reference point, which is located in the ground, setting this reference point we can measure the distance that Xavier traveled upwards the apple tree.
