The final select will be :

select * from(select descripcion as Provincia,count(provincia) as numero,

(Select count(provincia) from empresas where provincia not in
(select * from(Select provincia from empresas group by provincia order by count(provincia) desc)where rownum <=5)) as resto

from empresas,provincias
where empresas.provincia=provincias.codigo
group by provincia,descripcion order by count(provincia) desc)where rownum <=5;

The select in the middle is the 3rd field.If I execute it alone,it works,and if I execute the full select only with the first 2 fields,it works too...
The problem is when I try to execute the select with the 3 fields...