Answer:
or 
Step-by-step explanation:
We use casework on when
and when
.
For the first case,
, we add 9 to both sides to get
.
Dividing both sides by 3 gives

For the second case,
, we add 9 to both sides to get
.
Dividing both sides by 3 gives
.
Checking both cases, we plug in
and
.
For the first case, we have
, which satisfies the equation.
For the second case, we have
, which also satisfies the equation.
This gives us two solutions to the equation;
and
.