If the second term of an arithmetic sequence is -2 and the fourth term is 6, find the seventh term

We can find the common difference, d, between terms thusly :

d = [ 4th term - 2nd term ] / [4 - 2] = [ 6 - -2] / 2 = [8] / 2 = 4

So....the 7th term is given by

6 + 3d =

6 + 3(4) =

6 + 12 =

18