The expression d/t can be used to find the average speed of an object that travel a distance d in time t. What is sc cars average speed if it travels 145 miles in 2.5 hours?

You just divide the distance travelled by the time like so: 145mi/2.5h and get 58mph. You can convert the 145mi into meters and 2.5h into seconds (145mi is approximately 233345m; 2.5h is 9000 seconds) and get an approximate speed of 26m/s if you want to convert to SI units.