Final answer:
The solution to the inequality 21x - 12x > 54 is x > 6.
Step-by-step explanation:
The given inequality is 21x - 12x > 54.
To solve the inequality, we can combine like terms: 9x > 54.
Now, we can solve for x by dividing both sides of the inequality by 9: x > 6.
Therefore, the solution to the inequality is x > 6.