As you can see in the screenshot, once you plot the points for each rectangle, it becomes easier to see what's happening. In the first transformation, the rectangle is translated or slid. In the next 2 transformations, the rectangle is rotated. In the last transformation, the rectangle is dilated or shrunk. The first rectangle is the only translation.
Adding 1/9 to both sides, we get 2/3+y=8/9. Next, 2/3 can be multiplied by 3/3 to get 6/9 due to that 3*3=9 and using the identity property. We then subtract 6/9 from both sides to get y=2/9