Так?:

Program solution;
Uses Crt;
Var a, b, c : Integer;
s, k, y : Real;

begin
clrscr;

write('a, b, c: ');
readln(a, b, c);

s := (a + c * c * c * c) / (3 * b);
k := s - sqrt(abs(a + 2 * b * c * c * c * c));
y := a + 2 * b - (3 * s) / (b * c);

write(y : 0 : 4);

readkey;
End.

program sasha109

uses CRT;

var a,b,c:integer;

s,k,y:float;

begin

readln(a);

readln(b);

readln(c);

s:=(a+c*c*c*c)/(b*3);

k:=s-sqrt(abs(a+b*c*c*c*c*2));

y:=a+b*2-(3*s/(b*c))

writeln(y);

end.