Answer
The dimension of the rectangle is 6 inches (length) x 2 inches (width).
Work Step by Step
Let $x$ inches be the length of the rectangle
Since the width of the rectangle is 4 inches less than its length, the width = $x - 4$
Area = length x width
$12 = x \cdot (x - 4)$
$x^2 - 4x - 12 = 0$
$(x - 6)(x + 2) = 0$
$x = 6$ or $x = -2$ (rejected)
Therefore, the length = 6 inches and the width = 2 inches.
The dimension of the rectangle is 6 inches (length) x 2 inches (width).