Answer:
80
Step-by-step explanation:
Remark
Every triangle has a measure of 180 degrees.
Equation
Let the base angle = x
x + x + 2x-20 = 180
Solution
4x - 20 = 180
4x = 180 + 20
4x = 200
x = 50
Conclusion
Base angle 1 = 50
Base angle 2 = 50
Vertex angle = 2*50 - 20
Vertex angle = 100 - 20
Vertex angle = 80
