What is the reference angle for the given angle measure drawn in standard position?

−11π12

2pi - 11pi/12  = 

[24pi]/12 - [11pi]/12  =

13pi/12  *  180/pi  =

(13) (180/12)  =

13 * 15 =

195°  =   15°  in the 3rd quadrant

−23π6

4pi - 23pi/6 =

(24pi)/ 6 - (23pi)/6 =

pi/6  =  30°   in the first quadrant 

7π6

7pi/6  * 180 /pi  =   

7 (180/6) =

7* 30 =

210°

And  210  - 180  = 30°  in the 3rd quadrant