rails5-depot/app/views/line_items/_line_item.html.erb

<% if line_item == @current_item %>
  <tr id="current_item">
<% else %>
  <tr>
<% end %>
  <td><%= line_item.quantity %> &times;</td>
  <td><%= line_item.product.title %></td>
  <td class="item_price"><%= number_to_currency(line_item.total_price) %></td>
</tr>