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The given equation
|5x+9| - 3 = 13 (1)
is the same as the absolute value equation
|5x+9| = 16 (2) (a canonical form of a linear absolute value equation).
This last equation is equivalent to the system of two equations
5x+9 = 16 (3)
or
5x+9 = -16, (4)
connected by the service word OR.
Thus the given equation is equivalent to the system of two equations (B) and (C), connected with the service word OR.
It means that the set of solutions to equation (1) is the union of the sets of solutions to equations (3) and (4).
Solved, answered and explained.