Question

What's the lenght of side b in the figure below

Answer 1

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!