Hello, the undertaker!

Let the base beMary saw this notation: .

Mary thought it seemed to be incorrect.

She then realised that a number system other than decimal was used.

What is the base of that number system (with an explantion pls)?

Then represents: .

and represents: .

Then the equation is: .

Since is a root: .

. . and we have: .

The problem was written in base-seventeen.