According to the situation described, we have that:
a) The arithmetic sequence that gives the number of seats in the nth row is given by:

b) The 38th row has 290 seats.
<h3>What is an arithmetic sequence?</h3>
In an arithmetic sequence, the difference between consecutive terms is always the same, called common difference d.
The nth term of an arithmetic sequence is given by:

Item a:
The first row has 31 seats, the second has 38, the third has 45 and so on, hence:
- It is an arithmetic sequence.
- The common difference is d = 7.
- The first term is
.
Then, the rule is:



Item b:
This is the nth row, for which
, hence:





The 38th row has 290 seats.
You can learn more about arithmetic sequences at brainly.com/question/26366645