Hello guys I wanted to make a token system but I cannot add a custom number to a variable :/

Here is my code:
(Problem in line 9)

Code (Text):

1. command /eco [<text>] [<text>] [<text>]:
2.     trigger:
3.         if player has permission "tokenapi.eco" or "tokenapi.*":
4.             if arg-1 is set:
5.                 if arg-2 is set:
6.                     if arg-3 is set:
7.                         set {_add.%player%} to arg-3
8.                         wait a tick
9.                         add {_add.%player%} to {tokens.%arg-2%} #Here is my problem
10.                         send "{@prefix} &7Dir wurden &e%arg-3% &7Tokens überwiesen."
11.                         delete {_add.%player%}
12.             else:
13.                 send "Eroor 1"

Thanks a lot