To start, we know the basic equation from what us given:
[tex]c = 25 + mx[/tex]
And we want to find m. Fortunately, we have some numbers to plug in to find m. We can make an equation like this
[tex]67 = (210)m + 25[/tex]
by taking the amount charged and the amount of miles driven to get that charge given in the original problem.
Now we solve.
[tex]67 - 25 = 210m + 25 - 25 \\ 42 = 210m \\ \frac{42}{210} = \frac{210}{210} m \\ \frac{1}{5} = m[/tex]
Now we can put that in our equation to finish it.
[tex]c = \frac{1}{5} x + 25[/tex]
And that is the final equation
