If c(m)=0.50m+30 represents the cost of renting a car, how many miles were driven if the cost is $130?

M= the number of miles 
c= cost 
130(m)=0.50m+30 
subtract 30 on both sides 
100(m)=0.50m
divide .50 to isolate m
m=200

200 miles were driven if the cost is $130.

To solve, identify what each part of the equation means, plug 130 into the right part of the equation, and solve for m.

C(M) ⇒ Cost for renting a car
0.50M ⇒ Cost per mile driven
M ⇒ Miles driven
30 ⇒ Initial cost

Replace C(M) with 130 and solve for M.
130 = 0.50M + 30
100 = 0.50M
200 = M

So, if the cost is $130, 200 miles were driven.