Your answer would most likely be
B
The answers to the questions
Identify the property of equality which yields Step 1.
Well right off the bat, I can see a good reason why it should boggle.
If (x+y)=6 and (x-y)=2, then (x+y)(x-y) would be 12. It can't be 20.
The first 4 lines on the paper are inconsistent, so the question in the 5th line can't be calculated.
Another possible source of uncertainty (for us, anyway) is the remarkable similarity between the way you write ' Y ' and the way you write ' 4 ' . For example, look at the ' Y⁴ ' (I think ...) in the last line.
The area is 279. You do 11×19 to get the bottom portion. That will give you 209. Then for the top subtract 11 from 18 to get that side length and then do 7×10. With that you will get 70 and then you add 209 to that. 209+70=279.