Use Pythagorean's Theorem to find the length of x. [tex]30^2-16^2=x^2[/tex] so [tex]900-256=x^2[/tex] and [tex]x= \sqrt{644} [/tex]. We can simplify that radicand down into a perfect square times a prime number, and that is [tex] \sqrt{4*161} [/tex]. 4 is a perfect square that can be pulled out as a 2, so the length of x is [tex]2 \sqrt{161} [/tex], the choice on the top right.
