Find the measure of angle x when cos x is 12/13

If you have you calculator set to radians but you want degrees then anons answer is also correct. :)

arccos(12/13)*180/π, use the calculator, and π means pi, although it looks so weird.

acos(12/13)

$$\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{12}}}{{\mathtt{13}}}}\right)} = {\mathtt{22.619\: \!864\: \!948\: \!04^{\circ}}}$$