How do i find the reference angle of -11pi/3?

Answer is  π/3======reference angle is formed between a terminal arm of an angle and the x-axis. it's an acute angle.  the easiest way to do this question is to get the given angle in the range of    or, if we multiply the numerator and denominator of the range bounds by 3 to get a denominator of 3:     so if we add on  , we will make a coterminal angle which does not change the reference angle. keep adding  until it is within that range. (keep in mind that  is equivalent to  , but it has the same denominator as  so that's why we use that.)    is not in our needed range; do it again    is in our range, so we can base our reference angle answer off of that angle as it is coterminal to the original angle.well  is in the first quadrant. i know this because it is between  and  , or  and  .an angle in the first quadrant has a reference angle that is just the acute angle itself. the reference angle is  is just  therefore the reference angle of is 

Not so sure about this one sorry.