9514 1404 393
Answer:
63
Step-by-step explanation:
The number of seats in a row will give an arithmetic sequence:
6, 9, 12, 15, ...
The first term is 6; the common difference is 3. The general term is ...
an = a1 +d(n -1) . . . . . . n-th term of sequence with first term a1, difference d
The 20th term of the sequence is ...
a20 = 6 +3(20 -1) = 6 +57 = 63
There would be 63 seats on the 20th row.
