A trench needs to be at least 63 feet below ground level. This means it needs to be more than 3 1/2 times its current depth. This depth is represented by the inequality 3 1/2d<−63, where d is the current depth of the trench. Select from the drop-down to correctly interpret the solution of this inequality.

The current depth of the trench is

At most 18
Deeper than 18
less than 18
feet below ground level.