am assuming the text of the problem is:
"At 6:00 p.m., the temperature was 55 Fahrenheit. At 11:00 p.m. that same evening, the temperature was 40 Fahrenheit. What real number represents the average change in temperature per hour?"
Average change in temperature per hour = (55 - 40)/(11 - 6)
Average change in temperature per hour = 15/5
Average change in temperature per hour = 3 Fahrenheit per hour
