I am really struggling with this problem!!!

John decided to ride his bicycle across the country during his 3-month summer vacation.The route he took from Washington, DC to Portland, Oregon, covered a total of 3655 miles.To keep his mind occupied during some of the long flat stretches of countryside, he often did algebra problems in his head.One day, for example, he determined that his distance from his starting point was exactly 25 miles more than twice the distance remaining until the finishing point.How far was John from the finishing point of his journey when he made that calculation?Start your work by defining the unknown quantities in terms of a variable.