Answer: 5 units 
Explanation:
The shape presented is a triangle and the distance between Link and Ganon is the hypothenuse of that triangle. 
This can be calculate using the Pythagoras rule:
c² = a² + b²
c is the hypothenuse. 
a in the triangle = base = 4 units 
b = height = 3 units 
c² = 4² + 3²
c² = 16 + 9
c² = 25
c = √25
c = 5 units