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<!DOCTYPE html> <html> <body> <h1> This is my first calculator> <form method="post"> 1st<input type="number" name="x"><br> 2nd<input type="number" name="y"><br> <button type="submit" name="submit1" value="submit">addition</button> <button type="submit" name="submit2" value="submit">minus</button> <button type="submit" name="submit3" value="submit">multiply</button> <button type="submit" name="submit4" value="submit">devide</button> </form> </body> </html> <?php if (isset($_POST['submit1'])) { $x = $_POST['x']; $y = $_POST['y']; echo $x + $y; } if (isset($_POST['submit2'])) { $x = $_POST[...