What does a mod do?

It turns anything negative into a positive (it's an optimist :P).

So draw the graph of y = 3x - 6 over the domain.

Then reflect anything that's below the x-axis about the x-axis (in other words, make everything that's negative into a positive.)

Then you've got the graph of y = |3x - 6|.

Finally, you have to take the negative of this, so reflect the entire graph about the x-axis again.

Then you've got the graph of y = -|3x - 6|.

From your graph you should be able to tell for which values of x you have a y value less than -2.