index.html.erb # problems
========
<%= link_to "New problem", new_problem_solution_path(@problem), id: "new-solution-link", remote: true %>


solutions_controller
========
class SolutionsController < ApplicationController
  def new
    @step = Solution.new
    @step.problem_id = params[:problem_id]

    respond_to do |format|
      format.js
      format.html { redirect_to root_path }
    end
  end
end

new.js.erb
=========
$('#new-solution-link').hide().after('<%= j render("form") %>')

_form.html.erb
========
<%= form_for @step, remote: true do |f| %>
    <%= f.text_field :title %>
    <%= f.submit 'Ok'%>
<% end %>


routes.rb
========
resources :problems do
    resources :solutions
end