we have
[tex]\sqrt[3]{512m^{12}n^{15}}[/tex]
we know that
[tex]512=2^{9}[/tex]
substitute
[tex]\sqrt[3]{2^{9}m^{12}n^{15}}=({2^{9}m^{12}n^{15}})^{(1/3)}\\=(2)^{(9/3)}m^{(12/3)}n^{(15/3)} \\= 2^{3} m^{4} n^{5} \\= 8m^{4}n^{5}[/tex]
therefore
the answer is
[tex]8m^{4}n^{5}[/tex]