Run-time error: The input string was not well-formed. How to fix?

Question

Pascal

Unit Unit1;
interface
uses System, System.Drawing, System.Windows.Forms;
type
Form1 = class(Form)
procedure Form1_Load(sender: Object; e: EventArgs);
procedure button2_Click(sender: Object; e: EventArgs);
{$region FormDesigner}
private
{$resource Unit1.Form1.resources}
label1: &Label;
textBox1: TextBox;
label2: &Label;
textBox2: TextBox;
label3: &Label;
textBox3: TextBox;
label4: &Label;
label5: &Label;
label6: &Label;
textBox4: TextBox;
label7: &Label;
label10: &Label;
label11: &Label;
textBox6: TextBox;
label9: &Label;
label14: &Label;
label15: &Label;
textBox9: TextBox;
label12: &Label;
textBox7: TextBox;
label13: &Label;
button2: Button;
label8: &Label;
textBox5: TextBox;
{$include Unit1.Form1.inc}
{$endregion FormDesigner}
public
constructor;
begin
InitializeComponent;
end;
end;
implementation
procedure Form1.Form1_Load(sender: Object; e: EventArgs);
start
end;
procedure Form1.button2_Click(sender: Object; e: EventArgs);
var x, a, b, y : real;
begin
x := strtoint(textBox1.Text);
a := strtoint(textBox2.Text);
b := strtoint(textBox3.Text);
y := strtoint(textBox7.Text);
textBox5.Text :=FloatToStr((x*a+b)*50);
textBox9.Text :=FloatToStr ((((x*a+b)*50)/2058));
textBox6.Text :=FloatToStr (((((x*a+b)*50)/2058)+y));
end;
end.
Error in input line. Which? And where to find it?

Answer 1

And you enter only integer input data? (because ... strtoint ...)