What is the scale factor? Explaining how to solve this type of problem would also be appreciated!

Ricardo ran the 400 meter race 3 times his fastest time was 54.3 seconds his slowest time was 56.1 seconds if his average time was 55.0 seconds what was his time for the third race

Identify a1 and r for the geometric sequence an= -256(-1/4) n-1

What is r i 4.5+10r=-6.5 with work pls