Challenge 1: A grandparent/2 Rule Over Three Generations — Possible Solution
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family.pl:

parent(george, susan).
parent(susan, tom).
parent(tom, alice).

grandparent(X, Z) :- parent(X, Y), parent(Y, Z).

Query:

    ?- grandparent(george, tom).
    true.

    ?- grandparent(susan, alice).
    true.

    ?- grandparent(george, alice).
    false.

Explanation:
grandparent(george, tom) succeeds because parent(george, Y) can bind
Y = susan, and parent(susan, tom) is itself a genuine fact -- both
goals in the rule's body are satisfied, so the rule's head holds.
grandparent(george, alice) correctly fails, since george is alice's
great-grandparent, not her grandparent -- no single Y makes BOTH
parent(george, Y) and parent(Y, alice) true at once.

WHY THIS WORKS AS AN ANSWER
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This builds a real three-generation family using the chapter's own
parent/2 shape, defines grandparent/2 exactly as the chapter
introduces it, and queries both a true and a false case to confirm
the rule only succeeds for genuine two-generation gaps.