app/views/afiliacions/_form.html.erb
<%= simple_form_for(@afiliacion) do |f| %>
<%= f.error_notification %>
<div class="form-inputs">
<%= f.input :region %>
<%= f.input :hombres %>
<%= f.input :mujeres %>
<%= f.input :rangos %>
</div>
<div class="form-actions">
<%= f.button :submit %>
</div>
<% end %>