How to insert a CAPTCHA into your form?

Question

PHP

Hello! There is a form that sends data by post-method to the handler, and it writes them to the database.

<form action="action.php" method="post" id="myform"></form>
<table style="margin: 0 auto;" border="1">
<thead>
<tr>
<th>1</th>
<th>3</th>
<th>4</th>
<th>5</th>
<th>6</th>
<th>7</th>
</tr>
</thead>
<tbody>
<tr>
<td><input type="text" name="1" value="1" maxlength="10" size="20" form="myform" disabled></td>
<td><input type="text" name="2" value="13" maxlength="10" size="7" form="myform" disabled></td>
<td><input type="text" name="3" value="2" maxlength="10" size="10" form="myform" disabled></td>
<td><input type="text" name="4" value="3" maxlength="10" form="myform" size="15" disabled></td>
</td><td><input type="number" name="5" value="201" maxlength="10" size="17" form="myform" disabled></td>
<td><input type="number" name="6" maxlength="10" size="17" form="myform">
</tr>
</tbody>
</table>
<input type="submit" value="Отправить"  form="myform"/>

You need to insert a catcha-picture into this form ...
Please tell me how this can be implemented. Site on Wordpress.