Answer:
-7/10
Step-by-step explanation:
You can find the slope by using this formula: [tex]\frac{y-y}{x-x} \\[/tex] (rise over run!)
If you plug in the numbers, it looks like this: [tex]\frac{8-15}{20-10} \\[/tex]
Which simplifies to [tex]-\frac{7}{10}[/tex]