title: How to solve this context free grammar
body: <p>Give a Context free grammar for </p>
  
  <blockquote>
    <p>{<strong>w</strong> | <strong>w</strong> is an element of {a, b, c, d}* such that # of a+ # of b = # of c + # of D} </p>
    
    <p>how do i approach this question...?</p>
  </blockquote>