Looks like this in an incomplete question. I dug around the web (thanks to Google) and found something very similar on Test Magic. Mach, may be you can verify if this is indeed correct or not. The question should be:
(sqrt(9+sqrt80)+sqrt(9-sqrt80) )^2
Solution, which I know most of you will do with your eyes closed, is here:
Use the formula (a+b)^2 = a^2 + b^2 + 2ab
9+sqrt80+9-sqrt80 + 2*sqrt(9^2 - 80)
= 18 + 2*1 =20 (thanks to Mits83 from TestMagic)
For those who care, here is the link to the TestMagic thread:
https://www.urch.com/forums/gmat-problem ... p-2-a.html
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