don't really recommend dux for maths because there are people in there with wide range of abilities. Plus although dux say there classes are small for math they are not, believe me. For a person going to baulko this may be annoying as the tutor takes ages to come to you because some of your tutoring classmates are unable to understand simple concepts. I advice you to rather take 1 hour with a good private tutor instead of spending 2 hours with a tutoring company, ...will be cheaper and more effective.
p.s: dux are pretty good for their sciences though. They have got excellent tutors for those.