Lawrence A. answered 03/17/19
Patient and experienced tutor
The given sequence is an arithmetic sequence.
The first term is a = 31.
The common difference is d = 1.
The nth term is given by the formula
an = a + (n-1)*d
The last term (n-th term) is 131.
The number of terms, n, is given by
131 = 31 + (n-1)*1
131 = 31 + n-1
131 = 30 + n
131 - 30 = 30 + n - 30
101 = n
Answer: 101