Answer:
2485
Step-by-step explanation:
The number of seats in row n is given by the explicit formula for an arithmetic sequence:
an = a1 +d(n -1)
an = 20 +3(n -1)
The middle row is row 18, so has ...
a18 = 20 + 3(18 -1) = 71 . . . . seats
The total number of seats is the product of the number of rows and the number of seats in the middle row:
capacity = (71)(35) = 2485
The seating capacity is 2485.
