1. **State the problem:** Solve the logarithmic equation $$\log_5 (x - 18) - \log_5 x = \log_5 7$$ for $x$.
2. **Recall the logarithm subtraction rule:** For logarithms with the same base, $$\log_b A - \log_b B = \log_b \left(\frac{A}{B}\right)$$.
3. **Apply the rule to the left side:**
$$\log_5 (x - 18) - \log_5 x = \log_5 \left(\frac{x - 18}{x}\right)$$
4. **Rewrite the equation:**
$$\log_5 \left(\frac{x - 18}{x}\right) = \log_5 7$$
5. **Since the logs are equal and the base is the same, set the arguments equal:**
$$\frac{x - 18}{x} = 7$$
6. **Solve the equation:**
$$\frac{x - 18}{x} = 7$$
Multiply both sides by $x$:
$$\cancel{x} \cdot \frac{x - 18}{\cancel{x}} = 7x$$
$$x - 18 = 7x$$
7. **Isolate $x$:**
$$x - 7x = 18$$
$$-6x = 18$$
8. **Divide both sides by $-6$:**
$$\frac{-6x}{\cancel{-6}} = \frac{18}{\cancel{-6}}$$
$$x = -3$$
9. **Check the domain:**
The arguments of the logarithms must be positive:
- $x - 18 > 0 \Rightarrow x > 18$
- $x > 0$
Since $x = -3$ does not satisfy $x > 18$, it is not a valid solution.
10. **Conclusion:** There is no solution to the equation in the domain of the logarithm functions.
**Final answer:** No solution.
Logarithmic Equation D17986
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