<div id="rsvp-form-container">
  <div class="rsvp-left"> </div>

  <div class="rsvp-right">
    <h3> RSVP </h3>
    <%= form_tag('/guests/create', method: :post) do %>
      <%= render partial: '/guests/new' %>
      <div class="additional-guests"> </div>
      <a href="#" class="add-new-guest"> Add Another Guest </a>
      <div>
        <%= submit_tag 'RSVP' %>
      </div>
    <% end %>
  </div>
</div>

<div id="rsvp-form-container">
  <div class="rsvp-left"> </div>

  <div class="rsvp-right">
    <h3> RSVP </h3>
    <%= form_tag('/guests/create', method: :post) do %>
      <%= render partial: '/guests/new' %>
      <div class="additional-guests"> </div>
      <a href="#" class="add-new-guest"> Add Another Guest </a>
      <div>
        <%= submit_tag 'Mail In RSVP' %>
      </div>
    <% end %>
  </div>
</div>

Update rsvp form for spacing
Update rsvp form for spacing
