The temperature starts at 85 degrees.
t = 85
After 1 minute, it loses 3.5 degrees.
t = 85 - 3.5
After 2 minutes, it loses another 3.5 degrees.
t = 85 - 3.5 * 2
After 3 minutes, it loses another 3.5 degrees.
t = 85 - 3.5 * 3
etc.
After 12 minutes, it loses another 3.5 times 12 degrees.
t = 85 - 3.5 * 12