Basic simplification walk through

       + <
    /     \
   *        *
 /  \     /  \
4    5   2     3

       + 
    /     \
   * <       *
 /  \     /  \
4    5   2     3

       + 
    /     \
   20       * <
          /  \
         2     3

       + <
    /     \
   20       6

      26 <