Answer: The equation would NOT help us solve for the length and width of the classroom is "
".
Explanation:
Let y be the width of the rectangular classroom floor and x be the length of the rectangular classroom floor .
Given ,
The perimeter of a rectangular classroom floor is 90 feet.
The length of the floor is twice the width.
i.e. Length =2 (width)
i.e. x= 2y ..(i)
Also, perimeter = 2(length+width)
When we put value of x from (i), we get

Hence, the equation would NOT help us solve for the length and width of the classroom is "
".