Answer:
0, Below is the diagram for reference.
Explanation:
Let us assume hiker is starting from origin.
Positive [tex]y-axis[/tex] represents 'North'.
Positive [tex]x-axis[/tex] represents 'East'.
Negative [tex]y-axis[/tex] represents 'South'.
Negative [tex]x-axis[/tex] represents 'West'.
Hiker is starting from [tex]O[/tex], travels [tex]4\ km[/tex] on [tex]+x-axis[/tex], then [tex]6\ km \ down[/tex] (negative [tex]y-axis[/tex]), then [tex]4\ km[/tex] to the [tex]west[/tex](negative [tex]x-axis[/tex]), again [tex]6km[/tex] up.
Then he reaches the same starting point O.
