title: Racket language change & module problems
body: <p>I'm trying to implement some of SICP graphic programs in Racket, but there are 2 problems:</p>
  
  <p>When I need to use 'let' I can't use beginner language.
  When I try to change language, or open new file while using "advanced" language, I get this error:</p>
  
  <pre><code>module: identifier already imported from a different source
  </code></pre>
  
  <p>error when I try to load image module by (require 2htdp/image).</p>
  
  <p>What's going on? Also, are there better ways to train with images in Scheme?</p>