Answer
Factor $5$ out of each column, or, factor $5$ out of each row.
Work Step by Step
$$
\left|\begin{array}{rrr}{5} & {0} & {10} \\ {25} & {-30} & {40} \\ {-15} & {5} & {20}\end{array}\right|=5^{3}\left|\begin{array}{rrr}{1} & {0} & {2} \\ {5} & {-6} & {8} \\ {-3} & {1} & {4}\end{array}\right|.
$$
Factor $5$ out of each column, or, factor $5$ out of each row.