3p - 6 > 21 <=> 3p > 21+6 <=> 3p > 27 <=> p > 27/3 <=> p > 9. So the answer is B. When solving inequalities the idea is to move the terms which contain the unknown quantity to one side and the rest of the terms to the other side. And then perform valid mathematical operations to find the interval value for the unknown quantity.
