4 out of every 5 vehicles are cars, so 1 out of every 5 vehicles is a bus.<br><br>&bull; Fraction of buses = 1 &minus; \(\frac{4}{5}\) = \(\frac{1}{5}\)<br>&bull; Number of buses = \( \frac{1}{5} \times 45 = 9 \)<br><br>Final Answer: 9