X= 50 this is found due to triangles always equaling 180 degrees.
That would mean you got 7 right. 7/10 or 70% would be your grade.
Step-by-step explanation:
40° + 90° + 90° + angle ACB = 360°
220° + angle ACB = 360°
angle ACB = 360° - 220°
Therefore angle ACB = 140°
Hope it will help :))