A runner dashes from the starting line (x = 0) to a point 125 m away and then turns around and runs to a point 27 m away from the starting point in 27 seconds. To the nearest tenth of a m/s what is the average speed?

Distance travelled = 125 + (125-27) = 223 m

Divide that by the elapsed time, 27 s. I get 8.26 m/s. Round that to 8.3 m/s, since they say so.

This is the average SPEED (which does not depend upon direction), NOT the average velocity, which is less (1.0 m/s).

Your instructor may have a different interpretation.