## Elementary Technical Mathematics

$-\dfrac{9}{10}$
Use the rule $\frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}$. Note that the product and quotient of two numbers with different signs is negative. $\require{cancel} =\dfrac{4}{5} \times \left(-\dfrac{9}{8}\right) \\=\dfrac{\cancel{4}}{5} \times \left(-\dfrac{9}{\cancel{8}^2}\right) \\=-\dfrac{1(9)}{5(2)} \\=-\dfrac{9}{10}$