title: Calculating VAT backwards always returns as 0 in c#
body: <pre><code>public string s()
  { 
    double price = 123.12
    double preVatPrice = (100 / (100 + 20) + price);
  
    return preVatPrice.ToString();
  }
  </code></pre>
  
  <p>in c# this always returns as '0' any ideas why?</p>