Answer
12.2
Work Step by Step
Use the Pythagorean Theorem to find the missing length.
$a^2+b^2=c^2\longrightarrow$ substitute the given values
$2.2^2+12^2=c^2\longrightarrow$ simplify exponents
$4.84+144=c^2\longrightarrow$ add
$148.84=c^2\longrightarrow$ find the square root of each side
$\sqrt{148.84}=\sqrt{c^2}\longrightarrow$ simplify
$12.2=c$
