Answer
$(x-6+7y)(x-6-7y)$
Work Step by Step
$x^{2}-12x+36-49y^{2}=$
recognize a perfect square in the first three terms
$=(x^{2}-2\cdot 6x+6^2)-49y^{2}$
$=(x-6)^{2}-49y^{2}$
$=(x-6)^{2}-(7y)^{2}$
this is a difference of squares,
$=(x-6+7y)(x-6-7y)$
