A triangles angles measure up to 180° so before finding x you must find the missing angle.
So lets make an equation:
180=22+23+a
(a is the missing angle)
So add 22+23=45
180=45+a
Subtract 45 from both sides to isolate A
180-45=45-45+a
135=a
135° is your missing angle
So now we have to find X
A straight line measures to 180° so now we subtract 135°(or a) from 180°
180-135=x
x=45
Therefore X is 45°