Here is a link to the image. http://www.ucl.ac.uk/language-centre/placement-tests/UPC/Maths/images/question14.jpg I first thought of dividing the sides by 4, but then realized that we cannot assume that. The hint they gave is: Try again. If the middle piece of each side of the square is y, we get a right-angled triangle all of whose sides can be expressed in terms of x and y. Then apply Pythagoras's Theorem.
may you please explain, I do not get it at all. What is y? and if y is the vertical line, then what is the base, hwo do we use pytahgorean theorm??