Answer: Total change= 36 seconds.
Step-by-step explanation:
Let Greg's initial running time be t seconds.
As Greg has decreased his running time by 1 tenth minute each week.
Now, 1 tenth of minute =[tex]\frac{1}{10}\times60=6\ seconds[/tex]
Thus In the first week, his running time = [tex]t-6[/tex]
In the second week, his running time =[tex]t-6-6=t-12=t-2(6)[/tex]
Similarly,
In the sixth week, his running time =[tex]t-6(6)=t-36[/tex]
Hence, the total change in time of running = 36 seconds