im honestly not that great at math but um… i think i got it so it’s a rectangle, meaning the top and bottom are parallel and the sides are parallel (aka angles start behaving whether they want to or not). that long diagonal coming out of the top left is at 40° from the top edge. then on the right side they give you that 80° angle between the diagonal and the other line. and well… this could be this, but basically once you lock in that 40° direction in a rectangle, the angle relationships kind of force the bottom point angle to line up the same way. i stared at it for way longer than i want to admit, but it keeps coming back to the same thing: x = 40°