Write the Word or Phrase That Best Completes Each Statement $\sqrt [ n ] { 7 x - 5 } = \sqrt [ m ] { - 1 - 6 x }$

Write the word or phrase that best completes each statement or answers the question.
Provide an appropriate response.
-What is the smallest power to which you can raise both sides of the radical equation $\sqrt [ n ] { 7 x - 5 } = \sqrt [ m ] { - 1 - 6 x }$ so that the radicals are eliminated. Assume that $m$ and $n$ are relatively prime.
A) $\mathrm { mn }$
B) $\frac { 1 } { m } + \frac { 1 } { n }$
C) $\frac { \mathrm { m } + \mathrm { n } } { \mathrm { mn } }$
D) $m + n$