By definition, the area of a rectangle is given by:
 A = (width) * (long)
 Substituting values we have:
 750 = (y-5) * (y)
 Rewriting we have:
 750 = y ^ 2 - 5y
 y ^ 2 - 5y - 750 = 0
 Answer:
 An equation that can be used to solve for And the length of the room is:
 y ^ 2 - 5y - 750 = 0