I agree to the terms provided by the form.

Code

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <script>var jQ = $.noConflict(true);
// version 1
jQ(document).ready(function () {
//jQ("input[name='agree_text']").hide();
jQ("input[name='do_you_agree[]']").on('click', function() {

if (this.checked) {

jQ("input[name='agree_text']").val("I agree to the terms provided by the form.");
}else{
jQ("input[name='agree_text']").val("");

}
});
});</script>

Copy the above code to an HTML element. Change the name of the inputs in my code to match yours. If you don't use a checkbox like I did remove the [] to the right of the checkbox input name in the two spots it's used.