The exercise asks us to describe the behavior of the given procedure:
(define (a-plus-abs-b a b)
((if (> b 0) + -) a b))
The return value of the procedure can be described as follows
This is because the expression (if (> b 0) + -) evaluates the predicate (> b 0) and if it is true, returns the operator +, else, returns the operator -.
Sukrit Kalra 
Or more simply, a + abs(b); as hinted by the name of the function. xD
That is not an explanation for the given procedure. 😛
Show some basic code manipulations?
(define (a-plus-abs-b a b) ((if (> b 0) + -) a b))to
(define (a-plus-abs-b a b) (+ a (if (> b 0) b (- b))))to
(define (a-plus-abs-b a b) (+ a (abs b))) ;where (define (abs b) (if (> b 0) b (- b)))OT: Scheme programmers use 2-space tabs normally.