[tex]\bf 12^{2x-8}=15\\\\
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log_{{ a}}\left( x^{{ b}} \right)\implies {{ b}}\cdot log_{{ a}}(x)\impliedby thus\\\\
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log\left( 12^{2x-8} \right)=log(15)\implies (2x-8)log(12)=log(15)
\\\\\\
2x-8=\cfrac{log(15)}{log(12)}\implies 2x=\cfrac{log(15)}{log(12)}+8\implies
x=\cfrac{\frac{log(15)}{log(12)}+8}{2}[/tex]