I'm confused.
guest, were you responding to Cal?
Yes it is definitely a Pythorean question
BUT
Why is anyone multiplying by 2.5?
Here is the question:

Here is the answer:
Pythagoras's Theory
In any triangle, if the square on the longest is equal to the sum of the squares on the other 2 sides then the triangle MUST be right angled.
In this triangle, the square on the longest side is 13^2 = 169
and
the sum of the squares on the other two sides is 5^2+12^2= 25+144 = 169
since they are equal this has to be a right-angled triangle.