Hello
my problem is how to reduce decimal number of column in the tables. Problem is that some numbers are quotients and they have a lot of decimal which make a problem in the report where they have to have just 2 decimals.
Column in the query and in the report is not reserved only for numbers.
if some one have idea?

You can use the Format() and Round() functions to display these numbers any way you choose.

that seems good solution, how do I use this function?

Have you looked up the functions in VBA help yet? Help shows you the syntax to use the functions. You can use them in the ControlSource of your controls on the reports.
=Round([YourField],2)
...as an example.

thanks for quick answer, and is it possible to do it in the table?

Number fields have Format and Decimal Places properties if you need them but I prefer to leave those properties alone and set them when I display the value in either a form or a report. Just my $0.02.

It is also possible to constrain and format the output of a field in a query and use the query as the input to a report rather than a table.