Nice try, but still wrong.
You are making an erroneous assumption. You're saying the problem needed to be simplified and then you're complicating it by ADDING something that was not there to begin with, i.e. the assumption that the poser of the problem meant to include a stipulation that is clearly not there.
The FIRST RULE of mathematics is that you NEVER assume facts not in evidence.
The problem was quite simple:
what is 783 -344 + 92 x 70 = ?
You have to work left to right AND you have to work with what you have. You cannot assume that additional information was left out, which is what you're doing when you add the brackets. If you work strictly left from right, you get the answer I already showed AND I can defend that because I haven't made any assumption of facts NOT in evidence.
Sorry, 6th. You might be able to defend your solution by stretching the rule you quoted above, but I still firmly believe my answer is correct. (And, BTW - so does my brother, who has a degree in math).