Divide by 7.
... |-7x -3| = 3
Unfold to two equations.
... -3 = -7x -3 . . . . . the content of the absolute value is negative
... 0 = -7x . . . . . . . . add 3
... 0 = x . . . . . . . . . . divide by -7
and
... 3 = -7x -3 . . . . . . the content of the absolute value is positive
... 6 = -7x . . . . . . . . add 3
... -6/7 = x . . . . . . . . divide by -7
The solutions are ...
... x = -6/7 or x = 0
_____
Many graphing programs will happily tell you the locations of x- and y-intercepts, so it is convenient to rewrite the equation so its value is zero at the solution points. We can do that by subtracting the right side constant to get ...
... 7|-7x -3| -21 = 0