Unfortunately, limitations of the browser used by Answers.com means that we cannot see most symbols. It is therefore impossible to give a proper answer to your question. Please resubmit your question spelling out the symbols as "plus", "minus", "times", "equals", "squared" etc. I suspect there should be a symbol between x2 and 2x but cannot be sure what it might be.
Let there be x pupils in the class.Total increase in marks =x x1=x22x= (83 - 63) x= 20 x= 40.22