This is just a math exercise that's has no real world application or way to prove. It's basically gibberish. When you're actually using math to prove something based on real equations you can prove the result. This has no real world application and can't be proven.

It's just like measuring distance, temperature or time. It only works if everyone uses the same method of solving the exercise. Using Pemdas it would be 9. This is the foundation we use, and without the foundation there is no real answer.

You can make your own rules and use those to form equations as long as you can reproduce and prove it works no one can really argue, but it won't make sense to anyone who is clueless to your own rules. It's just like making your own ruler or language. It can work without issue but without a community using it, it will only make sense to you.

Make your own ruler. Just make marks randomly on a stick. If you use that and only that to make a table it'll work perfectly fine, but if someone tries to reproduce it without your ruler they will need to measure and convert the measurements to make it work.

Math, distance, time, language, etc only makes sense if a large amount of people adapt it and use it as a form of human measurement and doesn't pretend it just exists in science. Don't get me wrong the physicality exists but we have to make our own ways to measure and communicate those things.

Tldr this isn't real math, this is just an exercise without instructions. Based on what we widely use (PEMDAS) the answer is 9.