What’s the quotient of

20 divided by 1/4 \(= \frac{20}{\frac{1}{4}} = 20 *4 = 80\)

9/10 divide by (-4/5)  \(= \frac{\frac{9}{10}}{\frac{1}{4}} = \frac{9*4}{10*1} = \frac{36}{10} = \frac{18}{5}\) or 3.6