The equation is 
Write two cases:
\Case-1:
.

Case-2: 
Solve the equation for Case-1.
\
Subtraction property of equality: if
, then
.
(Subtract 4 from each side)
(Apply Additive inverse property:
)
(Subtract:
)
Check:
\To check the solution, substitute
in original equation.

(Add:
)
The absolute value of
is 17.

Compare the values the equation is true.
is a solution.
Solve the equation for Case-2.
\Subtraction property of equality: if
, then
.

(Subtract 4 from both sides)
(Subtract:
)
Check:
\To check the solution, substitute
in original equation.

(Add:
)
(The absolute value of
is 17)
Compare the values the equation is true.
is a solution.
The solutions are 13 and-21. The solution set is
.