$1.$

uses crt;

var a,b:integer;

begin

clrscr;

readln(a,b);

write(a+b);

readln;

end.

${2}.$

uses crt;

var a,b,c:integer;

begin

clrscr;

readln(a,b,c);

writeln(a+b-c);

readln;

end.

$3.$

Uses crt;

Var a,b:real;

Begin

Clrscr;

Readln(a);

Readln(b);

Writeln((a+b)/(a-b));

Readln

End.

$4.$

Uses crt;

Var r:real;

Begin

Clrscr;

Writeln('nhập bán kính: ');

Readln(r);

p:=2*r*pi;

s:=r*r*pi;

Writeln('chu vi hình tròn: ',p);

Writeln('diện tích hình tròn: ',s);

Readln

End.

Câu 1:

program tong;

uses crt;

var a, b : integer;

begin

clrscr;

write('nhap so nguyen a :');readln(a);

write('nhap so nguyen b :');readln(b);

writeln('tong hai so nguyen la :', a+b);

readln

end.

Câu 2:

program hieu;
uses crt;
var a, b : integer;
begin
clrscr;
write('nhap so nguyen a :');readln(a);
write('nhap so nguyen b :');readln(b);
writeln('hieu hai so nguyen la :', a-b);
readln
end.

Câu 3:

program chia;
uses crt;
var a, b : integer;
begin
clrscr;
write('nhap so nguyen a :');readln(a);
write('nhap so nguyen b :');readln(b);

writeln('gia tri bieu thuc la :', (a+b)/(a-b));

readln

end.

Câu 4: 

Program Hinh_tron;
Uses crt;
Var r, cv, dt : real;
Begin
Clrscr;
Write ('Nhap ban kinh hinh tron: ');
Readln (r);
cv := 2*pi*r;
dt := r*r*pi;
Writeln('Chu vi hinh tron la : ', cv);
Writeln('Dien tich hinh tron la :', dt);
Readln
End.