Add 'mathjax-rails' gem

config/routes.rb

@@ -4,6 +4,8 @@ Rails.application.routes.draw do
   end
   resources :translations, only: [:index, :show]
 
+  mathjax 'mathjax'
+
   # The priority is based upon order of creation: first created -> highest priority.
   # See how all your routes lay out with "rake routes".