The 2015 Southeast Asian Games used a mix of new, existing and temporary venues. Given the city-state's compact size, most venues were pre-existing public-sporting facilities located in the suburban heartlands which were reverted to public use after the games. No major retrofitting work were done in most venues as most had been used to host major multi-disciplinary events such as the 2010 Youth Olympic Games. At the centrepiece of the activities was the Singapore Sports Hub which was completed in mid-2014. Incorporating the new 55,000-seat national stadium, it hosted most of the events. A games village was not built. Instead, a "village in the city" concept saw athletes and officials housed in 20 hotels in downtown Singapore. Besides being physically near to the Singapore Sports Hub, it was hoped that it will add vibe to the city and reduce post-games costs in converting a dedicated games village to other uses. The 28th Southeast Asian Games had 30 venues for the games.

Based on the above article, answer a question. How many Southeast Asian Games happened prior to 2015?
27