$a)$

Program Hinh_chu_nhat;

uses crt;

var a,b,S,P: integer;

begin

writeln('Nhap chieu dai:');

readln(a);

writeln('Nhap chieu rong:');

readln(b);

P:=((a+b)*2);

S:=(a*b);

writeln('Dien tich la:',S);

readln

end.

$b)$

program BT2;
ues crt
var x:array [1..20] of integer;max,i:integer;
begin
clrscr;
writeln('nhap gia tri cho x:');
for i:=1 to 8 do
begin
write('x,'i,'=');readln(x[i]);
end;
writeln('cac phan tu cua mang la:');
for i:=1 to 8 do
write(x[i],'  ');
writeln;
max :=x[i];
for i:=2 to 8 do
if x[i] > max then max:=x[i];
writeln ('GTLN :,'max);
readln;
end.

$c)$

program tinh_gia_tri;
uses crt;
var a,b:integer;
      c:real;
begin
clrscr;
writeln('nhap vao so nguyen a: ');readln(a);
wirteln('nhap vao so nguyen b: ');readln(b);
c:=(a+b)/2;
writeln('gia tri cua bieu thuc: ',c:4:2);
readln
end.