Answer:
93,675
Explanation:
We see that the given sequence is an arithmetic sequence with first term 997, common difference -5, and last term 252.
The number of terms in the sequence (n) can be found from the formula for the n-th term:
an = a1 +d(n -1)
(an -an)/d +1 = n
(252 -997)/(-5) +1 = n = 150
The sum of these terms is the average of the first and last terms, multiplied by the number of terms:
S150 = (997 +252)/2·150 = 93,675
The sequence sum is 93,675.