Solve for x. (x)/(4)=(9)/(x) A. 36 B. 18 C. 2 or -2 D. 6 or -6 E. 4 or -4

To solve the equation $\frac{x}{4} = \frac{9}{x}$, we can cross-multiply to get $x^2 = 36$. Taking the square root of both sides, we find that $x = 6$ or $x = -6$. Therefore, the correct answer is D. 6 or $-6$.