Solution to Exercise 2.2:

`(define (make-segment start end)`

(cons start end))

```
```(define (start-segment s)

(car s))

(define (end-segment s)

(cdr s))

(define (make-point x y)

(cons x y))

(define (x-point p)

(car p))

(define (y-point p)

(cdr p))

(define (avg a b)

(/ (+ a b) 2))

`(define (midpoint-segment s)`

(let ((start (start-segment s))

(end (end-segment s)))

(make-point (avg (x-point start) (x-point end))

(avg (y-point start) (y-point end)))))