Screen shot
Route
Route::get('input','InsertDataModel@input');
Route::post('add_number','InsertDataModel@add_number');

Controller

<?php
namespace App\Http\Controllers;

use Illuminate\Http\Request;

class InsertDataModel extends Controller {
public  function input(){
return view('user_form');
}

public  function add_number(Request $request){
$number1 = $request->input('number1');
$number2 = $request->input('number2');
$number3 = $number1+$number2;
echo $number3;
}

}

View
<html>
<head>
<title>User Input Form</title>
</head>
<body>
<form name="frm"  action="add_number"  method="post">
<input type="hidden"  name="_token"  value="<?php echo csrf_token() ?>">
<table>
<tr>
<td>Number 1</td>
<td><input type="text"  name="number1"  value=""/></td>
</tr>
<tr>
<td>Number 2</td>
<td><input type="text"  name="number2"  value=""/></td>
</tr>
<tr>
<td colspan="2"  align="center">
<input type="submit" value="Submit" />
</td>
</tr>
</table>
</form>
</body>
</html>

You can download source code here