Might be a duplicate of this one:
To answer your question, my main study resource is Linux Academy's Ansible video course. I also plan to use Sander's Ansible Fundamentals live lessons, and official Ansible documentation. This should cover the exam objectives.
@ricardodacostaA Red Hat solution is basically RHLS, but unless you can afford it, you inevitably search for external resources that are cheaper. I'm not promoting LA or Sander's material here, but let us be fair, these video courses are decent, and, this is the most important part, affordable.
I haven't taken the exam myself, but here's a list of good resources I put together for my team that I’ve found useful:
http://docs.ansible.com/ - The on-line documentation
https://galaxy.ansible.com/ - Community site for playbooks
https://medium.com/@DefionsCode/30-lies-puppetlabs-made-about-ansible-25-will-shock-you-4fdd177b8bc6 - Explains some of the myths around Puppet vs Ansible
The Ansible YouTube channel: https://www.youtube.com/channel/UCeImQ-jeVhzgLJd9wsqo8Sg
There are also some on-demand webinars and training available:
I won't guarantee how current all of these are, but it should help get you started.