Answer:
77.7 °
Explanation:
So this uses the sum of interior angles, which in a rectangle, is 360°.
Now, we have two regular right angles, in the top and bottom right corners. Those angles measure 90° each. 90° + 90° = 180°.
Now we got the top left corners angle, so all that is left to do, is to subtract the three given corners angles, and the remaining is the angle for x.
So: 360° - 180° - 102.3 = 77.7°
So angle x = 77.7° :)
Hope this helped a bit!