2 3 *  rappresenta  2*3 = 6
4 6 +  rappreenta  4+6 = 10
4 2 3 * +  rappresenta  4 + 2 * 3 = 10
4 2 3 + *  rappresenta  4 * (2 + 3) = 20

1 2 3 4 5 - - - -  rappresenta  1-(2-(3-(4-5))) = 3
1 2 3 4 5 6 7 - - - - - -  rappresenta  1-(2-(3-(4-(5-(6-7))))) = 4

25 15 + 7 3 + - 10 / 5 +    ->    8

(25+15)-(7+3)
------------- + 5
      10

3 4 * 2 5 + / 5 4 + *    ->    15.428571428571427

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

5 3 2 / 4 * +    ->    11
  
   |+|
  /   \ 
 /     \                3
5       |*|        5 + --- * 4
       /   \            2
      /     \ 
    |/|      4
   /   \
  /     \ 
 3       2

1 2 * -3 * 4 5 - / 6 7 * +    ->    48

          |+|
         /   \
      |/|     |*|
     /   \    / \
  |*|    |-|  6 7
  / \    / \
|*|  -3  4 5
/ \
1 2

57.5 -34.1 - 6 3.2 / * 4.3 +    ->    176.05

                    6
(57.5 - (-34.1)) * --- + 4.3
                   3.2

15 7 1 1 + - / 3 * 2 1 2 + - -    ->    10

15 / (7 - (1 + 1)) * 3 - (2 - (1 + 2))