the volume of a rectangular prism is represented by 12x^3. The height is represented by 3x. Which of the following represents the area of the base?
$$\begin{array}{rll} V&=&A\times h\\\\ 12x^3&=&A\times 3x\\\\ \frac{12x^3}{3x}&=&A\\\\ A&=&\frac{12x^3}{3x}\\\\ A&=&4x^2\\\\ \end{array}$$