Answer:
y = 150º
Step-by-step explanation:
The sum of internal angles of a triangle must be 180º and the sum of y + (x-20) forms a straight line which is also 180º, so:
2x + x + (x - 20) = 180
4x - 20 = 180
4x = 200
x = 50
x - 20 = 50 - 20
x - 20 = 30
y = 180 - 30
y = 150º
