I suppose you meant to write
(x - 7)² = 16
Expand the left side:
x ² - 14x + 49 = 16
Subtract 16 from both sides:
x ² - 14x + 33 = 0
Factor the left side:
(x - 11) (x - 3) = 0
Now use the zero product property to conclude that either
x - 11 = 0 or x - 3 = 0
so that
x = 11 or x = 3
