The concession stand at the high school football stadium sells hot dogs and hamburgers to raise money for the high school athletic programs. Each hot dog sold earns the programs $0.50, and each hamburger sold earns $0.75. This week, the concession stand sold a combination of 230 hot dogs and hamburgers and earned $138.50 for the athletic programs. If x represents the number of hot dogs sold and y represents the number of hamburgers sold, which system of equations represents this situation?