The equation has two solutions 'cause of that Square in the expression, when you'll eliminate it, it would create two solutions, one with positive and one with negative:
(x - 6)² - 3 = 13
(x - 6)² = 16
x - 6 = _+ 4
x = -4 + 6 OR x = 4 + 6
x = 2 OR 10
Hope this helps!
