title: Getting NaN when adding variables which consists of another variables
body: <pre><code>var dml = 30
  var dd = parseFloat(document.getElementById("DriverD").value)     &lt;----- Only numbers like 10
  var dm = dd-dml
  
  alert((dd - dml) * 0.75)    &lt;----- This works
  alert(dm * 0.75)            &lt;----- This returns NaN
  alert(typeof(dm))        &lt;----- This show that dm is a Number
  </code></pre>
  
  <p>I'm not sure why I keep getting NaN. I already tried <code>parseFloat</code> and <code>parseInt</code> but still showing NaN when multiplying a variable (dm) which consists of variables (dd-dml). dm is the result of subtracting dml with dd or 10-30. Please share your solutions.</p>
  
  <p>I'm new here and I need help, please don't troll :) I am trying to add a cost calculator to my website. </p>