Đây!

Câu 2:

program C2;
uses crt;
var n,x,T:integer;
Begin
    clrscr;
    write('Nhap n = ');readln(n);
    While ( N <> 0 ) do
    Begin
        x:=n mod 10;
        n:=n div 10;
        T:=T + x;
    End;
    writeln('Tong cac chu so cua = ',T);
    if T mod 3=0 then write('La boi cua 3')
    else write('Khong la boi cua 3');
    readln
End.

Câu 3:

Program C3;
Uses crt;
Var     a,b,c,s,p : real;
Begin
    Clrscr;
    Write('nhap a = ');readln(a);
    Write ('nhap b = ');readln(b);
    Write('nhap c =');readln(c);
    If ((a+b)>c)and((b+c)>a)and((a+c)>b) then
    begin
        p:=(a+b+c)/2;
        s:=sqrt(p*(p- a)*(p-b)*(p- c));
        Writeln('Chu vi tam giac: ',2*p:4:2);
        Writeln('Dien tich tam giac: ',s:4:2);
    end
    else
    write(a:2:1,',',b:2:1,',',c:2:1,' khong phai la ba canh cua tam giac');
    Readln;
End.