Answer:
18
Step-by-step explanation:
The general formula for an arithmetic progression is a(n) = a(0) + d(n - 1), where a(0) is the first term,n is the index (counter), and d is the common difference between terms.
Here we have a(n) = -28 + (1/3)(n - 1)
and the 139th term is a(139) = -28 + (1/3)(138) = -28 + 46 = 18
