Ok guys, i was trying a not to hard calculation in flash… 
// var calc, with dot. Output: 25, ok, true…
nummer=10*2.5;
trace(nummer);
// var calc, with comma. Output: 20, where did the .5 go?
nummer=10*2,5;
trace(nummer);
// direct trace, with dot. Output: 25, ok, true…
trace((10*2.5));
// direct trace, with comma. Output: 5, should be 20, when i look above…, but why 5 this time?
trace((10*2, 5));
read the comments…