Solve for -1/3h< or = 6

An important thing to note with inequalities is that the inequality always flips when you multiply or divide both sides by a negative.
So you have,
-1/3h ≤ 6
and you multiply both sides by -3 to get
h ≥ -18
You can treat it like an equality usually, but that rule I stated above is important to remember.

Dwould be the answer