The lengths of the sides of a triangle with positive area are $\log_{10} 12$, $\log_{10} 75$, and $\log_{10} n$, where $n$ is a positive integer. Find the number of possible values for $n$.
1. Given the side lengths of a triangle are $\log_{10} 12$, $\log_{10} 75$, and $\log_{10} n$, we need to ensure that these lengths satisfy the triangle inequality. The triangle inequality states that the sum of the lengths of any two sides must be greater than the length of the remaining side.

2. We start by writing the triangle inequalities for the given side lengths:
   \[
   \log_{10} 12 + \log_{10} 75 > \log_{10} n
   \]
   \[
   \log_{10} 12 + \log_{10} n > \log_{10} 75
   \]
   \[
   \log_{10} 75 + \log_{10} n > \log_{10} 12
   \]

3. Simplify each inequality using the properties of logarithms:
   \[
   \log_{10} (12 \cdot 75) > \log_{10} n
   \]
   \[
   \log_{10} (12 \cdot n) > \log_{10} 75
   \]
   \[
   \log_{10} (75 \cdot n) > \log_{10} 12
   \]

4. Convert the inequalities from logarithmic form to exponential form:
   \[
   12 \cdot 75 > n
   \]
   \[
   12n > 75
   \]
   \[
   75n > 12
   \]

5. Solve each inequality:
   \[
   12 \cdot 75 = 900 \implies n < 900
   \]
   \[
   12n > 75 \implies n > \frac{75}{12} = 6.25
   \]
   \[
   75n > 12 \implies n > \frac{12}{75} = 0.16
   \]

6. Since $n$ must be a positive integer, the relevant inequalities are:
   \[
   6.25 < n < 900
   \]

7. The possible integer values for $n$ are from 7 to 899. To find the number of possible values, we calculate:
   \[
   899 - 7 + 1 = 893
   \]

The final answer is $\boxed{893}$.