To simplify the expression \( (15^6)^2 \) using the power rule of exponents, we can apply the rule that states \( (a^m)^n = a^{m \cdot n} \).
Here, we have:
- \( a = 15 \)
- \( m = 6 \)
- \( n = 2 \)
So, we apply the power rule:
\[ (15^6)^2 = 15^{6 \cdot 2} = 15^{12} \]
Now, let's look at the options you provided:
- \( 15^{3} \)
- \( 15^{4} \)
- \( 15^{8} \)
- \( 15^{12} \)
The correct answer is \( 15^{12} \).