A rhombus is quadrilateral with all side of equal length. Thus a quadrilateral with all sides of equal length and all angles right angles is still a rhombus but it is also a square. It is also a quadrilateral, a rectangle and a parallelogram.
You should know that the middle number with the x is double the original number not in expanded form. You should also know that in the expanded form, the last number is the square of the original number. So square(26/2) = 169.
