Answer:
510
Step-by-step explanation:
The n th term of an arithmetic sequence is
[tex]a_{n}[/tex] = a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Here a₁ = 6 and d = 15 - 6 = 9, thus
[tex]a_{57}[/tex] = 6 + (56 × 9) = 6 + 504 = 510
