We have 3 cities, which are named and the statement tells us they go in this order
These cities are Portland, Tacoma and Seattle
The distance between Portland and Tacoma is 120 miles and the distance between Portland and Seattle is 145 miles
To determine the distance between Tacoma and Seattle we must subtract the distances.
Let's look at the following graph to understand this better
As seen in the graph, the distance between Tacoma and Seattle is the distance between Portland and Seattle minus the distance between Portland and Tacoma
[tex]145-120=25[/tex]
The answer is 25 mi
