Examples:
(union '(a b c) '(b d a)) = '(b d a c)
(diff '(a b c) '(b d a)) = '(d c)

(sortedUnion '(a b e) '(b c d)) = '(a b c d e)
(sortedDiff '(a b e) '(b c d)) = '(a e)

(define (findFirst x y) (if (pair? x) (if (y (car x)) (car x) (findFirst (cdr x) y))))

(define (gt5 x) (> x 5))

(define (findAll x y) (if (null? x) '() (if (y (car x)) (cons (car x) (findAll (cdr x) y)) (findAll (cdr x) y))))

(define (mycompose x y) (lambda (z) (x (y z))))

(define (dfs List Action) (if (pair? List) (begin (dfs (car List) Action) (dfs (cdr List) Action)) (Action List)))

(define (findFirst x y) (if (pair? x) (if (y (car x)) (car x) (findFirst (cdr x) y))))

(define (gt5 x) (> x 5))

(define (findAll x y) (if (null? x) '() (if (y (car x)) (cons (car x) (findAll (cdr x) y)) (findAll (cdr x) y))))

(define (mycompose x y) (lambda (z) (x (y z))))

(define (dfs List Action) (if (pair? List) (begin (dfs (car List) Action) (dfs (cdr List) Action)) (Action List)))

(define (length List) (if (pair? List) (+ 1 (length (cdr List))) 0))

(define (pairs List) (if (pair? List) (if (pair? (cdr List)) (cons (list (car List) (cadr List)) (pairs (cdr List))) '()) '()))

(define (myequal L1 L2) (if (and (pair? L1) (pair? L2))

(and (myequal (car L1) (car L2)) (myequal (cdr L1) (cdr L2)))

(eq? L1 L2)))

(define (member x List) (if (pair? List)

(if (myequal (car List) x) #t (member x (cdr List)))

(eq? x List)))

(define (mynumber x Tree) (if (pair? Tree)

(if (myequal x (car Tree)) (+ 1 (mynumber x (cdr Tree)))

(+ (mynumber x (car Tree)) (mynumber x (cdr Tree))))

(if (myequal x Tree) 1 0)))

(define (mymult x y) (if (> x 0) (+ y (mymult (- x 1) y)) 0))

(define (mysublist x y) (if (eqfront x y) #t

(if (>= (length x) (length y)) #f

(eqfront x (cdr y)))))

(define (eqfront x y) (if (and (pair? x) (pair? y)) (and

(myequal (car x) (car y)) (eqfront (cdr x) (cdr y)))

(null? x)))