In order to calculate the rate, we calculate the variation of temperature and time
[tex]\begin{gathered} \Delta time=8-6 \\ \Delta time=2 \\ \\ \Delta temperature=-17-(-13) \\ \Delta temperature=-17+13 \\ \Delta temperature=-4 \end{gathered}[/tex]then, calculate the rate by dividing the variation of temperature by the variation of time
[tex]\frac{\Delta temperature}{\Delta time}=\frac{-4\degree C}{2h}=-\frac{2\degree C}{h}[/tex]the rate is equal to -2°C per hour, then from 8:00 pm to 11:00 pm, there is a difference of 3 hours.
Multiply the time by the rate:
[tex]-\frac{2\degree C}{h}\times3h=-6\degree C[/tex]The temperature drops another 6°C, then,
[tex]-17\degree C-6\degree C=-23\degree C[/tex]Answer:
The temperature will be about -23°C