Rails "no such file to load -- rubygems (LoadError)"

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http://stackoverflow.com – I just switched from Heroku to Amazon Web Services. Previously I ran all of my Rails command line commands using my Command Prompt with Ruby (from my Windows PC). However, after I logged into my Amazon Linux EC2 instance, and then went into the directory of my app I receive this error: /usr/bin/rails:9:in `require': no such file to load -- rubygems (LoadError) from /usr/bin/rails:9 when I try to run any commands like rails console. I reviewed this question, but it doesn't seem like multiple Ruby libraries apply to me because which -a ruby only yields one location: /usr/bin/ruby (HowTos)