So we know that vertical angles are congruent. So what we do to figure out x is set the equation equal to 110º because we are given that. And then we solve for x.
(13x + 45) = 110
13x + 45 = 110
-45 -45
----------------------
13x = 65
÷13 ÷13
---------------
x = 5
Now, we plug x into the equation. (13x5 + 45) = 110 so we know that x = 5
Now, we also know that a straight line equals 180º so what we do is subtract 110 from 180.
