Bài 11: 

program sosanh;
uses crt;
var a,b:integer;
begin
 clrscr;
 write('Nhap chieu cao ban a: '); readln(a);
 write('Nhap chieu cao ban b: '); readln(b);
 if a>b then writeln('Ban a cao hon') else writeln('Ban b cao hon');
 readln;
end.

Bài 12:

program tinh;
uses crt;
var a,b:integer;
begin
 clrscr;
 write('Nhap a: '); readln(a);
 write('Nhap b: '); readln(b);
 if b<0 then writeln('Phep chia khong thuc hien duoc') else writeln(a/b:0:3);
 readln;
end.

11.

var a,b:real;

begin

write('Nhap chieu cao ban a,b: '); readln(a,b);

if a>b then write('Ban a cao hon') else 

if b>a then write('Ban b cao hon') else

write('Hai ban cao bang nhau);

readln

end.

12.

var a,b:real;

begin

write('Nhap a,b: '); readln(a,b);

if b<0 the write('Phep chia khong thuc hien duoc') 

else write('Ket qua la: ',a/b:0:4);

readln

end.