Mr. Mole left his burrow that lies below the ground and started digging his way at a constant rate deeper into the ground. After 555 minutes of descending at a rate of 1.81.81, point, 8 meters per minute, he was 13.513.513, point, 5 meters below the ground. Let yyy represent Mr. Mole's altitude (in meters) relative to the ground after xxx minutes.

Complete the equation for the relationship between the altitude and number of minutes.

y=