what is an expression that can represent the area of the rectangular room? how can the expression be written in polynomial in standard form?show your work

The formula for determining the area of a rectangle is expressed as
Area = length * width
From the diagram,
Length = 3x + 6
Width = 4x - 1
The expression for the area of the room would be
[tex]\begin{gathered} (3x\text{ + 6)(4x - 1) = (3x }\times\text{ 4x) + (3x }\times-\text{ 1) + (6 }\times4x)\text{ + (6}\times-1) \\ \text{Area = 12x}^2\text{ - 3x + 24x - 6} \\ \text{Area = 12x}^2\text{ + 21x - 6} \end{gathered}[/tex]In standard polynomial form, the terms are arranged in decreasing order of exponents. Therefore, the expression in standard form is
[tex]12x^2\text{ + 21x - 6}[/tex]