>> Answer
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[tex] \: [/tex]
[tex] {16}^{x} = \frac{1}{64} [/tex]
[tex] \longmapsto{( {2}^{4} )}^{x} = \frac{1}{ {2}^{6} } [/tex]
[tex] \longmapsto { \cancel2}^{4x} = { \cancel2}^{ - 6} [/tex]
[tex] \longmapsto4x = - 6[/tex]
[tex] \longmapsto \: x = \bold{ - \frac{6}{4}} [/tex]
