Rewrite $ x^{2}-169 $ as:
$$ x^{2}-169 = (x)^2 - (13)^2 $$Now we can apply the difference of squares formula.
$$ I^2 - II^2 = (I - II)(I + II) $$After putting $ I = x $ and $ II = 13 $ , we have:
$$ x^{2}-169 = (x)^2 - (13)^2 = ( x-13 ) ( x+13 ) $$