# How do you multiplying rational expressions?

It's very easy: you only need to multiply numerators and denominators separately! So, the general formula is $\setminus \frac{a}{b} \setminus \cdot \setminus \frac{c}{d} = \setminus \frac{a c}{b d}$.
For example, if you want to compute $\setminus \frac{2}{3} \setminus \cdot \setminus \frac{4}{9}$, you simply get \frac{2 \cdot 4}{3\cdot 9} = \frac{8}{27