This is an arithmetic sequence. The expressive formula for an arithmetic sequence is aₙ = a₁ + (n-1)d, where a₁ is the first term and d is the common difference. In this case, a₁ = 12 and d = -1. We have aₙ = 12 + (n - 1) * (-1) = 12 - n + 1 = -n + 13. aₙ = -n + 13. Hope this helps!
