Explanation

Let's analyze the given inequality: k ≤ x ≤ 3k + 12

We can derive the following conclusions:

I. x - 12 ≤ 3k: Subtracting 12 from all parts of the inequality gives x - 12 ≤ 3k - 12 + 12, which simplifies to x - 12 ≤ 3k. (True)

II. k ≥ -6: Since k ≤ x and x ≤ 3k + 12, we can substitute x for k in the second part of the inequality, getting k ≤ 3k + 12. Subtracting 3k from both sides gives -2k ≤ 12, and dividing by -2 (which flips the inequality sign) gives k ≥ -6. (True)

III. x - k ≥ 0: Since k ≤ x, we can subtract k from both sides to get x - k ≥ 0. (True)

Since all three statements are true, the correct answer is: I, II, and III