```ruby
class Answer < ActiveRecord::Base
  include Voteable
  
  belongs_to :question
  belongs_to :author, class_name: 'User'
  has_many :comments, :as => :commentable
  has_many :votes, :as => :voteable

  validates :body, presence: true
end
```

Add time_since_creation method to Answer model
user
```ruby
class Answer < ActiveRecord::Base
  include Voteable
  
  belongs_to :question
  belongs_to :author, class_name: 'User'
  has_many :comments, :as => :commentable
  has_many :votes, :as => :voteable

  validates :body, presence: true

  def time_since_creation
    hours_number = ((Time.now - created_at) / 3600).round
    "#{hours_number} hours ago"
  end
end
```
assistant