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GitHub User: neoriddle
You are welcome :)
Maybe some one have tell you but if not I will.
I suppose is a little typo or error.
If you and see in your screencast at 04:30, you will watch this line:
<% f.fields_for :questions do |builder| %>
There is an error on <%, you must use <%=. It's a little issue but it could make you to spend a lot of time trying to solving it.
Greetings from Mexico