Challenge 2: Flatten and Filter — Possible Solution
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matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

evens = [n for row in matrix for n in row if n % 2 == 0]

print(evens)

Output:
[2, 4, 6, 8]

WHY THIS WORKS AS AN ANSWER
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for row in matrix for n in row reuses this chapter's own nested
comprehension shape exactly — for row in matrix is the outer loop,
for n in row is the inner one, read left to right in the same order
they'd appear as nested for loops, matching the chapter's own
flattening example and its loop-equivalent breakdown.

Adding if n % 2 == 0 at the end filters each individual number as it's
produced — n % 2 == 0 reuses the exact even-number modulo check from
Course 1, Chapter 4. Because the if comes after both for clauses, it
applies to n (the innermost, fully-flattened value), not to row —
this is what makes the filtering happen on individual numbers rather
than on whole rows.

Written as nested loops, this would be:
evens = []
for row in matrix:
    for n in row:
        if n % 2 == 0:
            evens.append(n)
which produces the same flattened-then-filtered result: only 2, 4, 6,
and 8 pass the even check out of all nine numbers in the matrix.