The first step to solving this would be to determine how many miles are represented by 1 inch:
15/2.5 = 6
1 inch = 6 miles
Now we want to know how far 4 inches is in miles:
6*4 = 24
Greenwood and Bay City are 24 miles apart
Hope this helps (also please mark me brainliest I only need 1 more to rank up)