Find the nth term: 13, 20, 27, 34

The ratio, r, is 20 - 13 = 27 - 20 = 34 - 27 = 7;

The nth term has the formula: an = a1 + (n-1) x r; where, a1 = 13 and r = 7;

Then, an = 13 + (n-1) x 7;

Finally, an = 13 + 7 x n - 7;

an = 7 x n + 6;