I need to get the exact solutions over the interval [0,2pi)

Sin 3x= -1

I have the intervals 0< x < 2pi

I am having trouble getting the first set of numbers with this inequality.

I have that the angle is 30 degrees of pi/6.

And the answer book says i should get

pi/6, 7pi/6, 13pi/6, 19pi/6, 25pi/6, and 31pi/6

I can get 4 of these by adding 2pi to each one, but i can't get 7pi/6 or 25pi/6.

Can anyone help? Thanks!