title: "Missing { inserted" keeps popping up in my code
body: <p>For line 14,17 it keep saying "Missing { inserted" but I don't know what does that mean.</p>
  
  <pre><code> \documentclass{article}
   \usepackage[utf8]{inputenc}
  
   \title{}
   \author{}
   \date{February 03 2019}
  
   \begin{document}
  
   \maketitle
  
   \section{Problem 1.11}
  
   Assume $a$ is irrational and $a^\sqrt{3}$ is rational.\newline
   Let's say $a = \sqrt[3]{x}$ and $x$ is a rational number.\newline
   If we square $a$ to $\sqrt{3}$, the result will be:\newline
   $(\sqrt[3]{x})^\sqrt{3}$ $= x$\newline
   Since $x$ is a rational number, therefore ,the proof is completed.
  
   \section{Problem 3.18}
  
   \end{document}
  </code></pre>