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Arithmetic expressions
Scheme uses fully parenthesized arithmetic expressions with prefix notation

Using prefix notation the operator is given before the operands

Expression

 Value

(+ 4 (* 5 6))
 
34
(define x 6)
(+ (* 5 x x) (* 4 x) 3)
 
207
(/ 21 5)
 
21/5
(/ 21.0 5)
 
4.2
(define (fak n)
  (if (= n 0) 1 (* n (fak (- n 1)))))

(fak 50)
 
30414093201713378043612608166064768
844377641568960512000000000000

There is no need for priorities - operator precedence rules - of operators in fully parenthesized expressions