Carla wants to save $55.50 to buy a new video game. Carla babysits her niece once a week and earns the same amount of money each week. After every time she babysits she donates $2 from the money she earned to the local food bank. Carla calculates that it will take her 6 weeks to save enough to buy her video game. Write and solve an equation to determine how much money Carla earns per week.