Find the index of element in list

I need to get index of element in list in scheme. For example:

(... 2 '(2 3 4 5))

0

(... 4 '(2 3 4 5))

2

Can someone help?

my final solution:

(define index
  (lambda (cislo l)
    (if (equal? (car l) cislo) 0 (+ 1 (index cislo (cdr l))))))
(define map-index-pred
  (lambda (pred? f l)
     (foldr (lambda (x y)
       (if (pred? (index x l))
         (cons (f x) y) (cons x y))) '() l)))