Составить программу для решения квадратного уравнения

uses crt;
var
x: integer;
begin
clrscr;
write ('vvedite ocenky: ');
readln (x);
if (x>=1) and (x<=3)
then writeln ('otnos k 1 yr')
else if (x>=4) and (x<=6)
then writeln ('otnos k 2 yr')
else if (x>=7) and (x<=9)
then writeln ('otnos k 3 yr')
else if (x>=10) and (x<=12)
then writeln ('otnos k 4 yr');
end.

uses crt;
var
x,l,m: integer;
begin
clrscr;
write ('vvedite 4islo (3-ex zna4): ');
readln (x);
l:=x div 100;
m:=x mod 10;
if l=m then writeln ('oni ravni')
else if l>m
then writeln ('Perva9 bolwe')
else writeln ('Posledn99 bolwe')
end.

uses crt;
var
d,a,b,c: integer;
x1,x2:real;
begin
clrscr;
write ('vvedite a (a<>0): ');
readln (a);
write ('vvedite b: ');
readln (b);
write ('vvedite c: ');
readln (c);
d:=sqr(b)+4*a*c;
if d<0
then writeln ('net korney')
else
begin
x1:=(-b+sqrt(d))/2*a;
x2:=(-b-sqrt(d))/2*a;
writeln ('x1=',x1:1:2);
writeln ('x2=',x2:1:2);
end;
end.

var x: integer;
begin
 writeln('Введите 12-ти бальную оценку: ');
 readln(x);
 if (x<=0)and(x>12) then writeln('Ошибка ввода!')
 else writeln('Уровень ученика: ',(x div 4)+1);
end.