Are you talking about the question that asked you to work out the perimeter? The little ‘x’ is quite clearly next to the short vertical. This question is actually a bit sneaky. You don’t actually need to know anything about ‘x’ to calculate the perimeter. It’s hard to explain in writing, but the perimeter of this shape is the same as if it was a simple rectangle. It gives you the lengths of the rectangle sides so the perimeter would just be (y + z) x 2 or more neatly 2y + 2z.
Hope this makes sense.