Question

angle BCD is an exterior angle of triangle ABC if angle BCD= 3x,angle A=x and angle B=80 .find the value of x

Answer 1

answer is 40.

x+80=3x (exterior angle property)

3x-x=80

2x=80

x=80/2

x=40

Answer 2

Sum of all sides in a triangle is equal to 180

So,,,
3x+x+80=180

4x+80=180

4x=180-80
4x=100
x=100/4
x=25

angle BCD is 3x======== = 3(25)=75
angle a = x= 25