The values that the actual temperature could be after the freezer was on for five minutes are 12°F or 18°F.
A trendline is sometimes referred to as a line of best fit and it is a statistical tool which is commonly used in conjunction with a scatter plot, in order to determine whether or not there's any form of correlation (either positive or negative) between a given data.
By critically observing the scatter plot, we can logically deduce that the trend line passes through the point (5, 15), which implies that the temperature is 15°F, 5 minutes after the freezer was turned on.
Since the actual temperature deviates by 3°F from what the trend line shows, we have:
Actual temperature = 15 ± 3
Actual temperature = 15 - 3 = 12°F
Actual temperature = 15 + 3 = 18°F