;; Number 1:

(define j (cons 'john 'lennon))
(define x j)
(set-car! x 20)

j --> (20 . lennon)



;; Number 2:

(define j (cons 'john 'lennon))
(define x (car j))
(set! x 20)

j --> (john . lennon)


;; Number 3:

(define j (cons 'john 'lennon))
(define x j)
(set! (car x) 20)

j --> ???
ERROR!!!!


;; Number 4:

(define j 'john)
(define l 'lennon)
(define (swap x y)
  (let ((temp x))
    (set! x y)
    (set! y temp)))
(swap j l)

j --> 'john


;; Number 5

(define j (cons 'john 'lennon))
(define (change x)
  (set! x 20))
(change (car j))

j --> (john . lennon)


;; Number 6

(define j (cons 'john (cons 'lennon nil)))
(def (change x)
     (let ((y (cadr x)))
       (set! y 20)))
(change j)

j --> (john lennon)


;; Number 7

(define j (cons 'john (cons 'lennon nil)))
(define (change x)
  (let ((y (cdr x)))
    (set-car! y 20)))
(change j)

j --> (john 20)

;; Problem 8:

(define j (cons 'john 'lennon))
(define a (cons j j))

(set-car! j 20)

a --> ((20 . lennon) 20 . lennon)

;; Problem 9:

(define l 'lennon)
(define j (cons 'john l))

(set! l 20)

j --> (john . lennon)