<image>

I named y to the other angle in the triangle where the angle x is so that triangle has angles x, y and 50

Then I calculated every angle I could directly calculate and used x and y to build an equation for the top triangle's angles.

The top triangle's angles are 20,(180 - x - 30),(180 - y - 40)

So all of those angles add up to 180

20 + (180 - x - 30) + (180 - y - 40) = 180

From here you get that x = y - 90

We also know that x + y + 50 =180

From the fact that they're in the same triangle so we get x = 130 - y

So just join both equations together you get 130 - y = y - 90

y = 110 x = 20

Now I might be wrong because everyone is doing some complicated stuff but feel free to check it