Well if the room is square then you ned to find the square root of the area.
Find 
Answer:
The value of the expression at w=3 is;

Explanation:
Given the expression;

Then when w=3, the value of the expression is;

The value is gotten by replacing/substituting w with 3 in the expression;
Therefore, the value of the expression at w=3 is;
X^3 - 21x = -20add 20 to both sidesx^3 - 21 x + 20 = 0Rational Root Theorem:Factors of P (constant) 20 = 1, 2, 4, 5, 10, 20------------------------------- Factors of Q (leading Coefficient) = 1
Possible zeros (all + -) 1/1, 2/1, 4/1, 5/1, 10/1, 20/1
Of the choices given only the number 1 is a possible root.