Display PHP within HTML values

What is the correct way to display a value in a link using php?

The (Advanced Custom Fields) php works correctly outside of the html.

Book on Expedia.com <a class="alignright" href="<?php the_field( 'expedia' ); ?>" target="_blank" ><input class="resume_contact_button" type="button" value="<?php the_field( 'low_rate' ); ?>"></a>