The range of a dataset is given by the greatest value minus the least value.
For last year's mean monthly temperatures, the greatest temperature is 29 and the least temprature is 6. Thus the range is 29 - 6 = 23.
For 2 years ago mean monthly temperatures, the greatest temperature is 25 and the least temperature is 7. Thus the range is 25 - 7 = 18.
Therefore, the difference in the range of temperature between the two years is 23 - 18 = 5.
