Fen completed a triathlon race whose total distance is DDD kilometers. First, she swam a distance of 0.50.50, point, 5 kilometer. Then, she rode a bicycle for xxx hours at an average speed of 202020 kilometers per hour. Finally, she ran for 0.50.50, point, 5 hour at an average speed of vvv kilometers per hour. Write an equation that relates DDD, xxx, and vvv.