By default, the ansible-playbook command is located at /usr/bin/ansible-playbook on Linux. The -v or --version option can be used to list the version of Ansible Playbook.

ansible-playbook --version

ansible-playbook 2.4.2.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/home/your_username/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible playbook module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible-playbook
  python version = 2.7.5 (default, mm dd yyyy, hh:mm:ss) [GCC 4.8.5 yyyymmdd (Red Hat 4.8.5-39)]