Problem: if 21 ! / 3 ^ x is an integer , what is the greatest possible value of x ?
Rationale: "21 - 7 * 3 18 - 3 * 3 * 2 15 - 5 * 3 12 - 4 * 3 9 - 3 * 3 6 - 2 * 3 3 - 1 * 3 hence max of 3 ^ 9 is allowed . imo d ."
annotated_formula: add(divide(21, 3), divide(3, divide(21, 3)))