Answer
13
Work Step by Step
Use the Pythagorean Theorem to find the missing length.
$a^2+b^2=c^2\longrightarrow$ substitute the given values
$5^2+12^2=c^2\longrightarrow$ simplify exponents
$25+144=c^2\longrightarrow$ add
$169=c^2\longrightarrow$ find the square root of each side
$\sqrt{169}=\sqrt{c^2}\longrightarrow$ simplify
$13=c$
