Challenge 3: Selecting "Everything Except the Face" From an Existing Selection — Solution Walkthrough

The approach:

With the face already selected using Lasso/Free Select, use Select >
Inverse (Photoshop) or Select > Invert (GIMP) to flip the selection so
that everything EXCEPT the previously selected face becomes the new
active selection.

Why this is more efficient than redrawing from scratch:

Per this chapter's own material on combining and reusing selections,
there's no need to manually trace the entire rest of the photo by
hand — inverting a selection is a single operation that takes whatever
is currently selected and swaps it for its exact opposite, reusing all
the careful, time-consuming work already done selecting the face
itself.

Why this isn't the same as the Shift/Alt modifier-key combination:

The Shift (add) and Alt (subtract) modifiers covered in this chapter
are for combining multiple selections made with the selection tools
directly, one region at a time. Inverting is a different, single-step
operation that flips an existing selection to its complement entirely
— exactly what's needed here, rather than trying to manually select
"everything else" region by region with the Lasso tool.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise checks that inverting a selection is recognized as the
efficient solution to a "select everything except this" problem,
correctly distinguishing it from the add/subtract modifier-key
combinations covered earlier in the same chapter.