Answer:
12x³
Step-by-step explanation:
The area (A) of a rectangle is calculated as
A = length × width
Here width = 12x and A = 144[tex]x^{4}[/tex] , thus
length × 12x = 144[tex]x^{4}[/tex] ( divide both sides by 12x )
length = [tex]\frac{144x^4}{12x}[/tex] = [tex]\frac{144}{12}[/tex] × [tex]\frac{x^4}{x}[/tex] = 12x³
