Respuesta :

Banabanana
Arithmetic sequence
a₁ = 13.1;  a₂ = 3.1;  a₃ = -6.9; a₄ = -16.9...   a₂₉ = ?

the common difference:
d = a₂ - a₁ = 3.1 - 13.1 = -10

29th term:
a₂₉ = a₁ + d(n-1)
      = 13.1 + (-10)(29-1)
      = 13.1 -10*28
      = 13.1 - 280
      = -266.9