To find \((f \cdot g)(x)\), we need to multiply the two functions \(f(x)\) and \(g(x)\):
- \(f(x) = x\)
- \(g(x) = x + 3\)
Now, we calculate: \[ (f \cdot g)(x) = f(x) \cdot g(x) = x \cdot (x + 3) = x^2 + 3x \]
The result, \(x^2 + 3x\), represents the area of the rectangle in square feet since the area \(A\) of a rectangle is given by the formula \(A = \text{length} \cdot \text{width}\).
Therefore, the correct response is: \((f \cdot g)(x) = x^2 + 3x; \text{ It represents the area of the rectangle in square feet.}\)