Let the first term be \(a\) and the common difference be \(d\).

The 12th term is given by:

\(a + 11d = 17\)

The sum of the first 31 terms is given by:

\(\frac{31}{2} (2a + 30d) = 1023\)

Solving the first equation for \(a\):

\(a = 17 - 11d\)

Substitute \(a\) in the second equation:

\(\frac{31}{2} (2(17 - 11d) + 30d) = 1023\)

\(\frac{31}{2} (34 - 22d + 30d) = 1023\)

\(\frac{31}{2} (34 + 8d) = 1023\)

\(31(34 + 8d) = 2046\)

\(34 + 8d = 66\)

\(8d = 32\)

\(d = 4\)

Substitute \(d = 4\) back into \(a = 17 - 11d\):

\(a = 17 - 44 = -27\)

The 31st term is given by:

\(a + 30d = -27 + 30 \times 4 = 93\)