SQL & PL/SQL

Hi,

Under Oracle 19c, I have a table and I want to count the total number of persons adding two columns : NOMBRE_ENFANTS and NOMBRE_ADULTES.

Here are the scripts :

CREATE TABLE ve_reservation_3 (
   "ID" INT,
   "NOM" VARCHAR(17) ,
   "PRENOM" VARCHAR(12) ,
   "COURRIEL" VARCHAR(32) ,
   "TELEPHONE" VARCHAR(15) ,
   "DATE_RESERVATION" DATE,
   "NOMBRE_ADULTES" INT,
   "NOMBRE_ENFANTS" INT,
   "COMMENTAIRES" VARCHAR(306) ,
   "NOMBRE_ANIMAUX" INT,
   "HEBERGEMENT" VARCHAR(8) ,
   "DATE_FIN_RESERVATION" DATE,
   "ADRESSE" VARCHAR(33) ,
   "ELECTRICITE" INT,
   "TOTAL" INT,
   "VEHICULE" INT,
   "NOMBRE_VEHICULES" INT,
   "PAYS" VARCHAR(51) ,
   "DON" INT,
   "PRIX" INT,
   "DATE_REGLEMENT" DATE,
   "MOYEN_REGLEMENT" VARCHAR(21) ,
   "REGLE" VARCHAR(9) ,
   "CREEE_LE" DATE,
   "CODE_POSTAL" VARCHAR(11) ,
   "VILLE" VARCHAR(16) 
);
***Moderator action: removed insert statements as they contain personal information (again). Please don't post names, phine number and mail addresses or any other vbalid personal data here!
Next Time the postwill be removed! ***

I have written a sql command but I don't know how to calculate the total number of persons :

select vr.hebergement,
      vr.date_reservation, vr.date_fin_reservation       
 from ve_reservation_3 vr
 where hebergement = 'Tente'
 group by vr.hebergement,  vr.date_reservation, vr.date_fin_reservation
 UNION
 select vr.hebergement,
      vr.date_reservation, vr.date_fin_reservation       
 from ve_reservation_3 vr
 where hebergement <> 'Tente'
 group by vr.hebergement,  vr.date_reservation, vr.date_fin_reservation

How to calculate the number of persons ? I want to have a result if this number is less than 20.

Best regards.