The given inequality :

Simplify :
Multiply both side by (-1) and reverse the inequality :

Divide the inequality by 3:

i.e. x is less than or equal to (-3)
Solution : x ≤ (-3)
so,
x is lies in the half open interval of - infinity to (-3)
Interval Notation : (-infinity, -3]
Answer:
Solution : x ≤ (-3)
Interval Notation : (-infinity, -3]