Final answer:
The expression in terms of x that represents the area of parallelogram PQRS is A = 25x^2.
Step-by-step explanation:
To find the area of parallelogram PQRS, we can use the formula A = base x height. In this case, the base of the parallelogram is one of the equal parts of the diagonal PR, which has a length of 5x. The height of the parallelogram is one of the equal parts of the diagonal QS, which also has a length of 5x. Therefore, the expression in terms of x that represents the area of parallelogram PQRS is A = (5x) x (5x) = 25x^2.