10) √((65,5² − 15,5²) / (13,5² − 11,5²))

\(65.5^2-15.5^2=(65.5-15.5)(65.5+15.5)=50\cdot81\).

\(13.5^2-11.5^2=(13.5-11.5)(13.5+11.5)=2\cdot25\).

\(\sqrt{\frac{50\cdot81}{2\cdot25}}=\sqrt{81}=9\).

Ответ: 9.