(I'm assuming we're finding the measurement of the smaller angle)
Let's say the smaller angle is x.
That means that the larger angle is 30 + 2x.
If we add the smaller and larger angle together, we get 180.
x + 30 + 2x = 180
Combine like terms
3x + 30 = 180
Subtract 30 on both sides
3x = 150
Divide 3 on both sides,
x = 50
So the smaller angle is 50 degrees :)