Answer:
Area of rectangle (A) is given by:

where, l is the length and w is the width of the rectangle.
As per the statement:
The area of a room is 396 square feet.
The length is (x + 8) feet and the width is (x + 4) feet.
⇒A = 396 square feet , l = (x+8) feet and w = (x+4) feet
Substitute these given values we have;

⇒
Combine like terms;
⇒
Subtract 32 from both sides we have;

or

⇒
⇒
⇒
By zero product property we have;
x+26 = 0 or x-14 = 0
⇒x = -26 and x = 14
Since, side cannot be in negative.
⇒x = 14
then;
l = x+8 = 14+8 = 22 feet
w = x+4 = 14+4 = 18 feet
Therefore, the dimensions of the room are:
l = 22 feet and w = 18 feet