Answer:
Explanation:
Angle 21 is calculated like this:
180 - 70 - 50 = 60 because a line is 180 degrees.
Angle 22 = 50 degrees because it is opposite to the upper angle of 50 degrees.
Angle 23 = 70 degrees because it is also opposite to the upper angle of 70 degrees.
The sum of the angles would be
60 + 50 + 70 = 180 degrees