title: Cannot install llvm-9 or clang-9 on Ubuntu 16.04
body: <p>I have not been able to install either llvm version 9 or clang version 9 on Ubuntu. We have installed them on Windows.</p>
  
  <p>I have tried a command and saw this response.</p>
  
  <pre><code>sudo apt-get install llvm-9
  Reading package lists... Done
  Building dependency tree
  Reading state information...
  Done E: Unable to locate package llvm-9
  </code></pre>
  
  <p>I have also tried and saw this response.</p>
  
  <pre><code>sudo apt-get install clang-9
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  E: Unable to locate package clang-9
  </code></pre>
  
  <p>My <strong>/etc/apt/sources.list</strong> file contains</p>
  
  <pre><code>deb http://apt.llvm.org/xenial/ llvm-toolchain-xenial-9.0 main
  </code></pre>
  
  <p>I found the website and saw that the folder was <strong>llvm-toolchain-xenial-9</strong>. Trying that version did not work either.</p>
  
  <p>What else can I do?</p>
  
  <p>I have looked at downloading the binaries but am not sure what installation steps I might be missing. I am not interested in compiling source code.</p>