To find the missing side \( x \) of a right triangle, we can use the Pythagorean theorem, which states that for a right triangle with legs \( a \) and \( b \) and hypotenuse \( c \):
\[ a^2 + b^2 = c^2 \]
Please provide the lengths of the known sides, and I can help you find the missing side \( x \).