Bài 1:
uses crt;
var a:array[1..100] of integer;
i,k,n,dem:integer;
begin
clrscr;
write('nhap k: '); readln(k);
write('nhap do dai mang: ');
readln(n);
for i:=1 to n do begin
write('nhap a[',i,']:');
readln(a[i]);
if a[i]=k then dem:=dem+1;
end;
writeln('co ',dem,' phan tu bang ',k);
write('vi tri cac phan tu la: ');
for i:=1 to n do if a[i]=k then write(i,' ');
readln
end.

Bài 2:
uses crt;
var s:string;
i:integer;
begin
clrscr;
write('nhap xau: ');
readln(s);
write('xau theo chieu nguoc lai: ');
for i:=length(s) downto 1 do write(s[i]);
writeln;
write('do dai xau la: ',length(s));
readln
end.