\[\boxed{\text{212\ (212).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[1)\ \left( n^{2} \right)^{8} = n^{2 \cdot 8} = n^{16}\]
\[2)\ \left( n^{9} \right)^{5} = n^{9 \cdot 5} = n^{45}\]
\[3)\ \left( \left( n^{3} \right)^{2} \right)^{10} = n^{3 \cdot 2 \cdot 10} = n^{60}\]
\[4)\ \left( n^{12} \right)^{4} \cdot \left( n^{21} \right)^{2} = n^{48} \cdot n^{42} =\]
\[= n^{48 + 42} = n^{90}\]