\(\dfrac{28^3\cdot5^{14}}{14^6\cdot25^7}\)
\(=\dfrac{4^3\cdot7^3\cdot5^{14}}{2^6\cdot7^6\cdot\left(5^2\right)^7}\)
\(=\dfrac{4^3\cdot7^3\cdot5^{14}}{2^6\cdot7^6\cdot5^{14}}\)
\(=\dfrac{\left(2^2\right)^3\cdot7^3}{2^6\cdot7^6}\)
\(=\dfrac{2^6\cdot7^3}{2^6\cdot7^6}=\dfrac{7^3}{7^6}=\dfrac{1}{\left(7\right)^3}=\dfrac{1}{343}\)
\(=\dfrac{4^3\cdot7^3\cdot5^{14}}{2^6\cdot7^6\cdot5^{14}}=\dfrac{1}{7^3}\)