title: How to run simple calculations in shell scripts
body: <p>i want to run the following</p>
  
  <pre><code>For i in A*.wav
  do
  soundstretch $i B$i -tempo=n
  done
  </code></pre>
  
  <p>but i wan n to be (2/(soxi -D $i)-1)*100.</p>
  
  <p>how do i code that?</p>