\[\boxed{\text{419\ (419).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{а)}\ x^{n} \cdot x^{3} = x^{n + 3}\]
\[\textbf{б)}\ a^{2} \cdot a^{m} = a^{2 + m}\]
\[\textbf{в)}\ x \cdot x^{n} = x^{1 + n}\]
\[\textbf{г)}\ y^{n}\ \ :y^{4} = y^{n - 4}\]
\[\textbf{д)}\ c^{9}\ :c^{m} = c^{9 - m}\]
\[\textbf{е)}\ k^{n}\ :k = k^{n - 1}\]