7. \(\dfrac{15^2\cdot3^2}{5^2}=\)

Представим \(15=3\cdot5\).

\(\dfrac{(3\cdot5)^2\cdot3^2}{5^2}=\dfrac{3^2\cdot5^2\cdot3^2}{5^2}=3^4=81\).

Ответ: 81.