... N>=3;Writeln(&apos ;Cac so Mersen <=',N,' la:');End;tuso:=tuso div a;mauso:=mauso div a;Write('Phan so p/q sau khi rut gon la ',tuso,'/ ',mauso);readln;END.21. ... }clrscr;Write('N=');readln(N);Writeln(N,' So tu nhien dau tien ma moi so trong chung');Writeln('khong chia het cho bat ky so tu nhien nguyen to');Writeln('nao khac ngoai cac so 2,3,5 la:');Num:=2;Count:=0;While ... b, USCLN: integer;Function USC(a,b:integer): integer;var so- du: integer;BeginWhile b<>0 doBegin so- du:= a mod b;a:=b; b:= so- du;end;USC:=a;end;write(' Cho hai số tự nhiên...