When running a 100-meter race Usain Bolt reached his top speed when he was 55 meters from the starting line and had been running for 4.6 seconds since the start of the race. He passed the 80 meter line of the race when he had been running for 7.8 seconds since the start of the race. Let
t
represent the number of seconds since the start of the race.

Let
d
represent Usain's distance from the starting line of the race.