In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data:
Geneva to Sparks
2.5 in
Sparks to Melville
4 inches
Scale
1 in = 15 miles
Distance = ?
Step 02:
Distance :
Scale:
1 in = 15 miles
Geneva to Sparks
2.5 in * ( 15 miles / 1 in) = 37.5 miles
Sparks to Melville
4 inches * (15 miles / 1 in) = 60 miles
Total distance = 37.5 miles + 60 miles = 97.5 miles
That is the full solution.