Answer:

m is the amount of miles driven, c is the total cost.
Explanation:
Since she has a flat fee of 1275, that's the 1275 in the equation and since we don't know how many miles she drives, that's the m in the equation for miles driven. Since each mile costs 0.20, that's the 0.2 in the equation. And since c is the total cost in dollars, that's the c in the equation.