Fix typo: variables->variable

Author: jasonflorentino

chapter11_variables.html

@@ -475,7 +475,7 @@ <h2 id='error_reporting'>Error Reporting</h2> <hr/>
 
 <p>We'll modify <code>lval_err</code> to act in the same way as <code>printf</code>, taking in a format string, and after that a variable number of arguments to match into this string.</p>
 
-<p>To declare that a function takes variables arguments in the type signature you use the special syntax of ellipsis <code>...</code>, which represent the rest of the arguments.</p>
+<p>To declare that a function takes variable arguments in the type signature you use the special syntax of ellipsis <code>...</code>, which represent the rest of the arguments.</p>
 
 <pre><code data-language='c'>lval* lval_err(char* fmt, ...);</code></pre>