Answer
$2\sqrt 6\approx4.899$
Work Step by Step
Step 1. Combine the left side to get $log_2[(x-4)(x+4)]=3 \longrightarrow x^2-16=2^3 \longrightarrow x^2=24 \longrightarrow x=\pm2\sqrt 6$
Step 2. Check, only $x=2\sqrt 6\approx4.899$ fits.
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