Q:

cal average speed

the following table represents the number of miles traveled per day by a hiker on his week-long excursion. Find the hiker's average speed in miles per day in the latter half of the week(days 4-7)
Day    0  1  2  3  4  5  6  7
Miles  0 15 10 12 7 12 18 21

A:

To compute the average speed per day you just need to sum all of the miles walked during those days and then divide by the number of days. In your case this amounts to
$$ \frac{7+12+18+21}{4} = \frac{58}{4} = 14,5 $$
Hence your hiker walked, during the last half of the week, with an average speed of $14,5$ miles per day.

