hey so i'm in 8th grade and am excelled in math... i'm in 10th grade math(geometry) and my teacher gave us a desmos activity (kinda like a pretest) and well there was this one question to find "X" and well i tend to over complicate things and did that here. in the picture you will see in the bottom right that i place 2 30 degree angles and assumed that it was split in half by the middle line, well my teacher saw that and told me that my answer was right, but he wanted to know how i did it, he saw i assumed those angles and kept on looking at it, well basically my question is "is there a principle describing that this is right? or some equation/method?"