We use the standard formulas for an arithmetic progression (AP). The nth term is given by a_n = a + (n-1)d, and the sum of the first n terms is S_n = n/2 (a + l) where a is the first term, d the common difference, and l the last term. These formulas are illustrated in the provided context (e.g., Example 14). For each series, we first determine a, d, and l, then find n using the nth term formula, and finally compute the sum.