Let's use Pythagorean theorem. \(a^{2}+b^{2}=c^{2}\) where \(c\) is the hypotenuse.
So if we set it up:
\(7^{2}+b^{2}=13^{2}\)
now we simplify:
\(49+b^{2}=169\)
and get \(b^{2}\) by itself:
\(b^{2}=120\)
Now to get \(b\) by itself, we need to take the square root of both sides:
\(b=\sqrt{120}\)
And that's your answer!
