Some general rules:
log(x) + log(y) = log(xy)
a^logₐ(x) = x
log₃(x-4) = 2-log₃(x+4)
log₃(x-4) + log₃(x+4) = 2
log₃((x-4)(x+4)) = 2
log₃(x²-16) = 2
x²-16 = 3²
x² = 25
x = ±√25 = ±5
The argument of a logarithm must be positive, so -5 is an extraneous solution.
x = 5