Bài 1:

program bt;
uses crt;
var A:array[1..1000] of integer;
    i,n,k,S,d:integer;
function snt(n:integer):boolean;
var i:integer;
 begin
  snt:=true;
  for i:=2 to (n-1) do if (n mod i=0) then
   begin
    snt:=false;
    break;
   end;
  if snt=true then write(n,' ');
  end;
begin
 clrscr;
 write('Nhap n: '); readln(n);
 write('Nhap k: '); readln(k);
 For i:=1 to n do
  begin
   write('Nhap phan tu thu ',i,': '); readln(A[i]);
   if A[i]>0 then
    begin
     inc(d);
     S:=S+A[i];
     end;
  end;
 writeln('Co ',d,' phan tu duong trong mang');
 writeln('Tong cac phan tu duong la ',S);
 For i:=1 to n do if a[i]=k then
  begin
   break;
   writeln('vi tri dau tien ma phan tu = k la ',k);
  end;
 write('Cac so nguyen to la : ');
 for i:=1 to n do if (a[i] mod 2 <>0)and(a[i]>2) then snt(a[i]);
 readln;
end.

Bài 2:

program xau;
uses crt;
var S,T,X:string;
    i:integer;
begin
 clrscr;
 write('Nhap xau S: '); readln(S); X:=S;
 while pos('  ',S)>0 do delete(S,pos('  ',S),1);
 if S[1]=' ' then delete(s,1,1);
 if S[length(S)]=' ' then delete(s,length(S),1);
 writeln('Xau S da xoa ki tu thua: ',S);
 For i:=1 to length(X) do if X[i] in ['0'..'9'] then T:=T+X[i];
 if (T<>'') then writeln('Xau S da xoa ki tu chu cai: ',T);
 readln;
end.

Program BTT;
Uses crt;
Var St: String;
    i: longint;
Begin
        Clrscr;
        Write('Nhap St: '); Readln(St);

        While St[1]=#32 do Delete(St,1,1);
        While St[length(St)]=#32 do Delete(St,length(St),1);
        While Pos(#32#32,St)<>0 do Delete(St,Pos(#32#32<St),1);

        For i:=1 to length(St) do
                If St[i]<>['0'..'9'] then Delete(St,i,1);
        Write(St);
        Readln
End.