(define (parse-sol T)
  (define (parse-sol-helper operator)
    (cond ((eq? operator #\+) +)
          ((eq? operator #\-) -)
          ((eq? operator #\*) *)
          ((eq? operator #\/) /)))
  (if (number? (value T))
      (value T)
      ((parse-sol-helper (value T))
       (parse-sol (left T))
       (parse-sol (right T)))))

(define example ( list #\+ ( list #\*
                                  (list 4 '() '())
                                  (list 5 '() '()))
                       (list #\+
                             (list #\/ ( list 6 '() '()) '())
                             (list 7 '() '()))))