Answer choice B.
The shorter leg is 5 units long, so it will be written as 5^2
And the other leg is 12 units long, so that will be written as 12^2
And finally the hypotenuse is 13 units long, which can be written as 13^2
Since this is about the Pythagorean Theorem, the equation will be 5^2 + 12^2 = 13^2
