Câu a:

uses crt;
var x,y:integer;
begin
        clrscr;
        write('nhap so x: ');readln(x);
        write('nhap so y: ');readln(y);
        x := y;
        y := x;
        writeln(x,' la so y sau khi hoan doi');
        writeln(y,' la so x sau khi hoan doi');
        readln;
end.

Câu b+c:

uses crt;
var a,b:integer;
begin
        clrscr;
        write('nhap so a: ');readln(a);
        write('nhap so b: ');readln(b);
        if a < b then write('a nho hon b')
        else write('a lon hon b');
        readln;
end.

Câu d:

HÌNH VUÔNG:

uses crt;
var a,b,s:integer;
begin
        clrscr;
        write('nhap so do canh hinh vuong: ');readln(a);
        s := a*a;
        b := a*4;
        writeln('chu vi hinh vuong la: ',b);
        writeln('dien tich hinh vuong la: ',s);
        readln;
end.

HÌNH CHỮ NHẬT:

uses crt;
var a,b,s,c:integer;
begin
        clrscr;
        write('nhap so do chieu dai hinh chu nhat: ');readln(a);
        write('nhap so do chieu rong hinh chu nhat: ');readln(c);
        s := a*c;
        b := (a+c)*2;
        writeln('chu vi hinh chu nhat la: ',b);
        writeln('dien tich hinh chu nhat la: ',s);
        readln;
end.