Answer
$36x^3$
Work Step by Step
We are given the rational expressions:
$$\dfrac{7}{9x^3}\text{ and }\dfrac{5}{12x}.$$
The Least Common Denominator of the rational expressions is obtained as the product of all factors which belong to the denominator's factor decomposition, taken at the highest exponent:
$$\begin{align*}
9x^3&=3^2\cdot x^3\\
12x&=2^2\cdot 3\cdot x.
\end{align*}$$
The Least Common denominator is
$$2^2\cdot 3^2\cdot x^3=36x^3.$$
