How long is ef? a. 20b. 25c. 30d. 35

Need this asap if anyone can i would be very grateful. if you could show workings that would really

The area of a rectangle is 54x^9y^8 square yards.if the length of the rectangle is 6x^3y^4 yards,which expression represents the width of the rectangle in yards

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36