Choice Dhoice C is the correct answer. We can model this with the equation $2x + 5 = 25$, where $x$ is the number of miles.

1. Set up equation: $2x + 5 = 25$
2. Subtract 5 from both sides: $2x = 25 - 5$
3. Simplify: $2x = 20$
4. Divide both sides by 2: $x = \frac{20}{2}$
5. Simplify: $x = 10$
6. Verify: $2(10) + 5 = 20 + 5 = 25$ ✓

So, the ride was 10 miles long.

Choice Dhoice D is incorrect because this results from adding 5 to 25: $30$, then $30/2 = 15$. You subtract the base fare, not add it.

Choice Dhoice C is incorrect because this is the cost of the miles ($20), not the number of miles.

Choice Dhoice A is incorrect because this results from dividing the total fare by the rate: $25/2 = 12.5$. This ignores the base fare.