Wei Yan had some marbles at first. He gave $$\frac{3}{8}$$ of them to his friends and $$\frac{5}{7}$$ of the remaining marbles to his brother. His cousin then gave him $$408$$ marbles. In the end, he had twice as many marbles as he had at first. How many marbles did Wei Yan have at first? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Finding the Base