Answer:
20²-(13²-5² )=y²
400-(169-25)=y²
400-144 =y²
256=y²
y=16
Explanation:
In the diagram above is a 2 right angle triangles
the length of such diagrams is found using the pythagoras theorem.
in finding the length of the vertical by pythagoras gives..(13²-5²)^-2=12