I need help on Pythagorean theorem

A^2 + b^2 = c^2
5^2 + b^2 = 13^2 (plug in numbers)
25 + b^2 = 169 (square the plug in numbers)
-25 = -25 (subtract 25 from both sides)
b^2 = 144 (find square root of 144)
b = 12 (this is answer)

B=12

Explanation:
First things first, identify the hypotenuse. That is the longest side of the triangle and the one opposite to the right angle.
Then, fill in the equation using substitution.
5 squared is 5(5) or 25
13 squared is 13(13) or 169
Now you have 25+b^2=169
Subtract 25 from 169 to get
b^2=144
Now to even out the statement and get rid of the exponent, find the square root of 144.
You will get b=12