Your answer is n=2. thank me if this helped you. :)
Differentiate the given solution:

Substitute
and
into the ODE:

and it's easy to see the left side indeed reduces to 0.
Answer:
x < -2
Step-by-step explanation:
12 - 6x > 24 Equation
-6x > 12 Subtract 12 from both sides
x < -2 Divide both sides from -2, if you divide by any negative number in an inequality you have to switch the sign