A cab company charges $5 per cab ride, plus an additional $1 per mile driven , How long is a cab rid

A cab company charges $5 per cab ride, plus an additional $1 per mile driven , How long is a cab ride that costs $13?

Let the number of miles driven be m. Our cost function C(m) is:
C(m) = Cost per mile * m + cab cost
C(m) = 1m + 5

The problem asks for m when C(m) = 13:
1m + 5 = 13

To solve this equation for m, we type it in our search engine and we get:
m = 8