Prefix Notation

I could do with some prefix notation practice (I have not reached Satori).

To this end, I'd be terribly obliged if you could post some nested mathematical expressions with nested brackets and only simple (+ - * /) operators, so I can practice converting them.

I'd also be obliged if you could tell me if I'm right/advise me where I'm going wrong.

An example;
7(8 x 9(10 x 3(8 + 4)))
(* 7 (* 8 (* 9 (* 10 (* 3 (+ 8 4 ) ) ) ) ) )

Am I right? Wrong? Advice?

(+ 4 1 ( * 3 7 ) (/ 2 4))
4 + 1(3 x 7)(2 / 4)
4 + (3 x 7)(2 / 4)

Sorry if it isn't clean, but this is the easiest format for me to read.

Solution is; 4 + 21 x 1/2 = 14.5(?)

(/ (+ 3 3 5) (- (* 2 5) (+ 4 6)))
(3 + 3 + 5)
           /
            (2 * 5) (4 + 6)

11 / 100 (Eleven hundredths)