Answer:
107
Step-by-step explanation:
Angle 1
When a line is passes through a straight line, the two angles must equal 180 degrees. Since you know the one angle is 81, then angle 1 is 180 - 81 or
99 degrees.
Angle 2
You can determine the angle that is opposite of the 91 angle. These two angles must add up to 180. So the angle to the right of 91 must be 89.
89 + 91 = 180
You were told lines c and d are parallel. Based on that, the angle you just calculated must be equal to angle 2 or 89 degrees.
Angle 3
Again, you know that lines c and d are parallel. When a line crosses over two parallel lines, the outer opposite angles would be equal to each other.
So angle 3 is equal to the angle marked as 81 degrees.
Angle 1 + Angle 2 - Angle 3 = 107
