I have
$$ \tan x < 2 $$
what are its solutions? (solution-set)
What I've done?
$$ \tan x -2 < 0$$
Now, by analysing the sign-change, or wavy-curve method
So $$ \tan x \in (- \infty, -2) $$
Now- how to find $x$?
EDIT: I would prefer an algebraic method, but in response to a comment I would like to add the required graphs

The simplest way is to help with a drawing:
We deduce the general solution: $$x\in\bigcup_{k\in\mathbf Z}\Bigl(\frac\pi2+2k\pi,\arctan 2+(2k+1)\pi\Bigr)\cup\Bigl(-\frac\pi2+2k\pi,\arctan 2+2k\pi\Bigr).$$