Answer:
m =-7/3
Step-by-step explanation:
[tex]\mathrm{Slope\:between\:two\:points}:\quad \mathrm{Slope}=\frac{y_2-y_1}{x_2-x_1}\\\\\left(x_1,\:y_1\right)=\left(0,\:21\right),\:\left(x_2,\:y_2\right)=\left(9,\:0\right)\\\\m=\frac{0-21}{9-0}\\\\m = \frac{-21}{9} \\\\Use\:3\:to\:divide\:through \\m=-\frac{7}{3}[/tex]
