To apply the Power Rule of Exponents, which states that \((a^m)^n = a^{m \cdot n}\), we can rewrite the expression \((15^6)^2\):
\[ (15^6)^2 = 15^{6 \cdot 2} = 15^{12} \]
Thus, the equivalent expression is:
15 to the power of 12 (or 15 superscript 12 baseline).