Since the absolute value of a number is the POSTIVE DISTANCE FROM ZERO, you can really have two answers |3| = 3 and |-3|=3
Therefor the expression inside the absolute value bars can equal either 3 or -3, so you need to set up two separate expresstions representing that fact.
Expression 1

Add 13 to both sides

Divide by 6

reduce

Expression 2

Add 13 to both sides

Divide by 6

reduce

So either answer will work, if you plug in the Expression 1, you will get
|3| which is 3, if you plug in Expression 2, you will get |-3| which is ALSO 3