Answer
$x$
$ \tan (90-x)^{\circ} = \cot x^{\circ}$
Work Step by Step
Using Cofunction Theorem-
$ \tan (90-x)^{\circ} = \cot x^{\circ}$
Reason-
tangent and cotangent are cofunctions and
$ (90-x)^{\circ} + x^{\circ} = 90^{\circ}$
i.e. $ (90-x^{\circ}$ and $ x^{\circ}$ are complementary angles.
