Answer:
[tex]\boxed{x=7, \: x=-13}[/tex]
Step-by-step explanation:
[tex]|3x+9|= 30[/tex]
Solve for absolute value.
There are two possibilities.
One possibility:
[tex]3x+9=30\\3x=21\\x=7[/tex]
Second possibility:
[tex]3x+9=-30\\3x=-39\\x=-13[/tex]