You don't "do" vertical angles, any more than you "do" triangles, fractions,
or arithmetic problems.
In order to answer a question or solve a problem, you must first understand
very clearly what the question is. In math, the question is almost always to
calculate or identify some unknown quantity. The way to "do" that is to take
the given information, then use what is known, together with all the rules and
procedures you know about the relevant operations, functions, or figures, to
find what is unknown.