Math question in the photo. Please help! Do not guess if you don’t know please!

How do i do this activity, is appreciated

Mozart lenses inc. recently introduced seelites, a thinner lens for eyelasses. of a sample of 800 eyeglass wearers, 246 said they would purchases their next pair of eyeglasses with the new lenses. lenses inc. estimates that the number of people who purchase eyeglasses in a year is 1,700,000. most eyeglasses wearer buy one new pair of eyeglasses a year. what is the annual sales potential for the new lenses.

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?