title: Calculating the sum of two variables in a batch script
body: <p>This is my first time on Stack Overflow so please be lenient with this question. I have been experimenting with programming with batch and using DOSbox to run them on my linux machine. </p>
  
  <p>Here is the code I have been using:</p>
  
  <pre><code>@echo off
  set a=3
  set b=4
  set c=%a%+%b%
  echo %c%
  set d=%c%+1
  echo %d%
  </code></pre>
  
  <p>The output of that is: </p>
  
  <pre><code>3+4
  3+4+1
  </code></pre>
  
  <p>How would I add the two variables instead of echoing that string?</p>