Since angles 1 and 2 are equal, we can form the following equation
20 - 8x = 30 - 16x
Now we need to isolate x in one side to find its value
Do this by adding 16x to both sides so the -16x moves to the left side
20 - 8x + 16x = 30 - 16x + 16x
20 + 8x = 30
Subtract 20 from both sides so the 20 in the left side disappears
20 - 20 + 8x = 30 -20
8x = 10
Divide both sides by 8 so x is alone in the other side
8/8x = 10/8
x = 10/8 or 5/4
Since we did all this to both sides, both sides are still equal and the equation still holds true
Hope it helps u if u didnt know how to this yet