Yes, that seems easier to me as well! I was not allowed to do this according to the teacher when I was a child. They wanted me to do it in some weird counterintuitive way. But I was very stubborn and I am still doing calculations in this way. She is not the boss of the way I think!

So, for me it is 10-8=2. Then 7-2=5. And then 10+5=15.

It is impossible to prove that it is the case that everything is fake and it is impossible that it isn’t. Lots of things like this we cannot know for sure. However, you parents being real, society being real etc is a less complex explanation than everything being a VR simulation. If you do not have additional information, then the less complex explanation often is the most likely. So, if you assume reality is not a simulation, you are more likely to be right.