The temperature at 1:00 pm on Tuesday was -13C. There was an increase of -6 per hour starting at 1:00 pm. Which of the following best represents the Celsius temperature n hours after 1:00 pm on Tuesday?
I am interpreting " an increase of -6 per hour" to mean a decrease of 6° per hour.
"Which of the following ..." has no following.
I would expect to see something like
temperature = -6t - 13,
where t is the number of hours past 1:00 pm on Tuesday.