How to find a if ab+c=bc-a? And what would be a good website to train working out these questions?

Need to find a by rearranging the equation ab+c=bc-a

First question is the most important. I just don't get it and need help at it ): It is the working I am interested in, so please not just answers.

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia…).