\( \begin{array}{ll}\text { а) } \frac{7}{8} \cdot \frac{9}{28} ; \quad \text { б) } \frac{18}{19}: \frac{27}{38} ; & \text { в) }\left(\frac{2}{3}\right)^{4} \cdot\left(\frac{3}{2}\right)^{4} .\end{array} \)

To solve \( \frac{7}{8} \cdot \frac{9}{28} \), you multiply straight across: \( \frac{7 \cdot 9}{8 \cdot 28} = \frac{63}{224} \). Simplifying by dividing both numerator and denominator by 63 gives \( \frac{9}{32} \). For \( \frac{18}{19} : \frac{27}{38} \), remember that dividing by a fraction is the same as multiplying by its reciprocal. So it’s \( \frac{18}{19} \cdot \frac{38}{27} \). We simplify this to \( \frac{684}{513} \), and after canceling by 171, we get \( \frac{4}{3} \). For \( \left(\frac{2}{3}\right)^{4} \cdot\left(\frac{3}{2}\right)^{4} \), notice that both fractions are inverses. Therefore, \( \left(\frac{2}{3} \cdot \frac{3}{2}\right)^{4} = 1^{4} = 1 \). Now you can impress your friends with your math magic!