ANSWER
The substitution property of equality.
EXPLANATION
We know that:

and that

Since x=5 or 5=x , we can substitute x for 5 wherever we see x in the given equation.
When we do that, we obtain;

This is what we refer to as the substitution property of equality.
A right triangles hypotenuse is the square root of both of the other side squared. The formula for this is a^2 + b^2= c^2, with c being the longest side. So 10 squared is 100, 13 squared is 169, but. 17 squared is 289. The sum of the other two sides are 269. So it doesn’t equal
563*(10*10*10) that's you scientific notation