The measure of angle B is equal to 60 degrees.
In order to find this, we can first note that the angle C (in the right side triangle) is equal to 80 degrees. We can tell this because it creates a straight line with the other angle C and therefore the two combined give us 180 degrees.
Then we can add angle A, B and C together in the right side triangle to get 180 degrees since they are all the measures of angles in a triangle.
A + B + C = 180
2x + 3x + 80 = 180
5x + 80 = 180
5x = 100
x = 20
Now that we have the x value, we can plug into the equation for B.
B = 3x
B = 3(20)
B = 60
