A lake near the Arctic Circle is covered by a 2-meter-thick sheet of ice during the cold winter months. When spring arrives, the warm air gradually melts the ice, causing its thickness to decrease at a constant rate. After 3weeks, the sheet is only 1.25 meters thick. Let y represent the ice sheet's thickness (in meters) after xxx weeks.
Complete the equation for the relationship between the thickness and the number of weeks.
the answers should be y=blank