Choice Ahoice C is the correct answer.

1. Start with the equation: $5x - 10 = 25$
2. Add 10 to both sides: $5x = 25 + 10$
3. Simplify: $5x = 35$
4. Divide both sides by 5: $x = \frac{35}{5}$
5. Simplify: $x = 7$
6. Verify: $5(7) - 10 = 35 - 10 = 25$ ✓

Choice Ahoice D is incorrect because this results from subtracting 10 from 25: $15$, then $15/5 = 3$. We must add to undo subtraction.

Choice Ahoice B is incorrect because this is the value of $5x$. Don't stop early!

Choice Ahoice C is incorrect because this results from multiplying 35 by 5: $35 \times 5 = 175$.