Given the arithmetic sequence that starts

−8, 10, . . .
(a) Find the 20th term of the sequence. (Given that −8 is the first term.)
(b) Find the sum of the first 37 terms of the sequence

the difference (between terms) is ... 10 - -8 = 18

(a) -8 + (19 * 18) = ?

(b) the 37th term is ... -8 + (36 * 18) = ?
... the sum is ... [-8 + (37th term)] * (37/2)