Hello, miley_22!

The first one involves an Arithmetic Progression.

The term of an Arithmetic Progression is:1. A theatre has 20 rows of seats. There are 15 seats in the 1st row, 17 seats in the

2nd row, and each successive row of seats has two more seats than the previous row.

a. Calculate the number of seats in the 20th row.

. .

where: .

We have: .

Therefore: .

The sum of the first terms of an Arithmetic Progression is:b. Caculate the total number of seats.

. .

Therefore: .