Final answer:
To find the scale of the map, set up a proportion between the distance on the map and the actual distance. However, without the correct scale value, we cannot determine the scale of the map.
Step-by-step explanation:
To find the scale of the map, we can set up a proportion. Let's call the distance between the airport and the shopping mall on the map x inches. According to the given information, the actual distance between these two places is 20 miles. So, we have the proportion:
x inches / 2.5 inches = 20 miles / x miles
To solve for x, we can cross multiply and then solve for x:
x * 20 miles = 2.5 inches * x miles
20x = 2.5x
20x - 2.5x = 0
17.5x = 0
x = 0 inches
However, an x value of 0 inches doesn't make sense in this context. Therefore, there must be an error in the map scale or the given information. Without the correct scale value, we cannot determine the scale of the map.