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log(x+6) < log(3-2x)
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Your staring inequality is
    log(x+6) < log(3-2x).
First, determine the domain, i.e. the set of real numbers, where this inequality makes sense.
Logarithm must have positive arguments:  x+6 > 0  and  3-2x > 0.
First inequality gives  x > - 6;  the second inequality gives  3 > 2x,  or   x < 1.5.
So, the domain is this set  -6 < x < 1.5.     (1)
Next, logarithm is monotonic function; therefore, from the given inequality we have
    x + 6 < 3 - 2x.
Simplify it
    x + 2x < 3 - 6
      3x   <   -3
       x   <   -1.
Comparing the domain (1) with the last inequality, we see that the solution to the problem is this set
    -6 < x < -1.
Solved.