Answer:
Total change = <em>x </em>- 36 seconds.
Step-by-step explanation:
Let Greg's initial running time be <em>x </em>seconds.
Also, 1/10 minute = 6 seconds.
In the first week, his running time = <em>x </em>- 6
In the second week, his running time = <em>x </em>- 6 - 6 = <em>x </em>- 2(6)
In the third week, his running time = <em>x </em>- 6 - 6 - 6 = <em>x </em>- 3(6)
....
....
In the sixth week, his running time = <em>x </em>- 6(6) = <em>x </em>- 36
Hence, the total change = <em>x </em>- 36.