Even if you have it, this worked to update to recent version:
gem install rails
gem install mysql2
If nvm already installed:
nvm install stable
currently using node v9.11.0 (npm v5.6.0)
npm install -g @angular/cli
Sarah Maas Carrie Edwards Colin Powell
To serve Angular app on C9 ng serve --open --host $IP --port $PORT --disable-host-check