[tex]3log\frac{x}{4}+3log\frac{x}{5}=5logx-log125 \\
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3\left(log\frac{x}{4}+log\frac{x}{5}\right)=5logx-log125 \\
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3\left(log\frac{x^2}{20}\right)=5logx-log125 \\
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3.\left(logx^2-log20\right)=5logx-log125 \\
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3logx^2-3log20=5logx-log125 \\
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6logx-log8000=5logx-log125 \\
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6logx-5logx=log8000-log125 \\
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logx=log\frac{8000}{125} \\
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\boxed{logx=log64 \rightarrow x=64}[/tex]