Answer:
x = 67°
Step-by-step explanation:
The little square in the corner represents 90° because it is a right-angle.
All angles in a triangle add up to 180°.
90° + 23° = 113°
180° (total) - 113° (whats already there) = 67° (x)
I hope this helps. If you need further explanation, let me know.
- profparis
