Q: what options are there?
A: You have a few options. You can either go with a tour company. The length of the trip will depend on who gives the tour, and what other stops there are. You can take a louage (long distance taxi identifiable by its white color and red stripe across the body) to Tunis and catch a taxi from there. The louage will take about 2.5 hours and the taxi will take about 20 mins. You can take the train from Sousse to Tunis and then take a taxi to Carthage once in Tunis. The length of time would be the same as if you took a louage. If I can be of any more help or assistance, please feel free to contact me.