Answer:
105
Step-by-step explanation:
In this triangle the arc marks at B and C indicate equal angles. Since a is 30 and a triangle must add to 180, you can subtract 30 from 180 and divide the result in 2. 180 - 30 = 150. 150/2 = 75. Each angle is 75.
The angle you need to know is outside the triangle. It forms a straight line with 75. Every straight line is 180. So if 75 is part of it, the rest is 180 - 75 = 105.
