Cannot install Vagrant due to discontinued "brew cask" command

[tuongtran23]

Problem

In Step 4 System Tutorial, when I get to Vagrant Tutorial page, I tried installing Vagrant in MacOS using command line
brew cask install virtualbox as instructed and the command generated error.

Steps to reproduce the problem

N/A

Screenshots

Proposed solution

The error from the terminal also suggests the solution, I have tried the new command as below and was able to install virtualbox:

brew install virtualbox --cask

In vagranttutorial.md, substitute all occurring no longer user brew cask install virtualbox with brew install virtualbox --cask