106 is the nth term for the sequence 1, 8, 15, 22...

nth = F + (N -1)D

106 =1 + (N-1)*7

106 =1 + 7N - 7

106 - 1 + 7 = 7N

112 = 7N divide both sides by 7

N = 112 / 7

N = 16th term in your sequence.

The common difference between terms is 7

So....we can solve this

106 = 1 + 7(n - 1) simplify

106 = 1 + 7n - 7

106 = 7n - 6 add 6 to both sides

112 = 7n divide both sides by 7

16 = n → i.e, the 16th term