Question 1039911
Since I saw the constant number to this sequence and that is 3, 

If the number is decreasing

this would be the formula
x-3

If the number is increasing

This would be the formula
x+ 3

If the sequence is 48, 45, 42, 39, ....... 30th term (Decreasing)
Or 30th term .......... 48, 45, 42, 39 (Increasing)

My answer are
Decreasing: -33
Increasing: 116


Sequence (If decreasing) : 48 , 45, 42, 39, 36, 33, 30, 27, 24, 21, 18, 15, 12, 9, 6, 3, 0, -3, -6, -9, -12, -16, -19, -21, -24, -27, -30, -33, -36, -33

In the decreasing the 30th term is -33


Sequence (If increasing): 116, 113, 120, 107, 104, 101, 98, 95, 92, 89, 86, 83, 80, 77, 74, 71, 68, 65, 62, 59, 56, 53, 50, 47, 44, 41, 48, 45, 42, 39

I hope I helped you