помогите решить несколько задач

Program Ex68;
uses crt;
var i:integer;
begin
clrscr;
for i:=10 to 99 do
if (i*2 mod 10 = 8 ) or (i*3 mod 10 = 4) then
writeln(i);
readln
end.

Program xa;
var
 y:real;
 x:longint;
begin
 Writeln('BBedute 4ucLo');
 readln(y);
 x:=round(y*1000);
 if (x mod 10=0) or (x div 10 mod 10=0) or (x div 100 mod 10=0) then
  Writeln('Ectb 0')
 else
  Writeln('Hety 0-L9');
 readln;
end.

Program xa;
var
 a,b,c:integer;
 x1,x2,d:real;
begin
 Writeln('BBedute a/b/c/d');
 Write('a=');
 readln(a);
 Write('b=');
 readln(b);
 Write('c=');
 readln(c);
 d:=b*b-4*a*c;
 if d<0 then
  writeln('KopHeu Het')
 else
 begin
  x1:=(-b-sqrt(d))/2*a;
  x2:=(-b+sqrt(d))/2*a;
  if x1=x2 then
   Writeln('KoPEhb 1-uH u PaBeH  ' ,x1)
  else
   Writeln('x1= ' ,x1:8:3, '   x2= ' ,x2:6:3)
  end;
 readln
end.

uses crt;
var a:real;
    b,c,k,i:integer;
begin
clrscr;
repeat
write('a=');readln(a);
until a>0;
b:=trunc(frac(a)*1000);
c:=0;
for i:=1 to 3 do
  begin
   k:=b mod 10;
   if k=0 then
     begin
      c:=1;
      break;
     end;
   b:=b div 10;
  end;
if c=1 then write('Yes!')
else write('No!');
readln
end.

Program Ex68;
uses crt;
var i,n:integer; d,a:real;
begin
clrscr;
writeln('vvedit n'); readln(n);
writeln('vvedit a'); readln(a);
d:=a; 
for i:=1 to n do d:=d*(a-i*n);
writeln(d:6:2);
readln
end.