To solve the equation \( x^2 - 121 = 0 \), you can first add 121 to both sides of the equation:
\[ x^2 = 121 \]
Next, take the square root of both sides:
\[ x = \pm \sqrt{121} \]
Since \( \sqrt{121} = 11 \), we find:
\[ x = 11 \quad \text{or} \quad x = -11 \]
Since the problem asks for the lesser number first, the final answer is:
\[ x = -11, \quad x = 11 \]