Exercise 2: Two Steps, Each Depending on Multiple Earlier Chapters — Possible Solution
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EXAMPLE PAIR: STEP 2 (SCANNING AN ITEM)
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Scanning a single item genuinely depends on three separate chapters working together, not one: Chapter 5 supplies the client-side decoding that turns a camera image into a barcode string; Chapter 4 supplies the lookup view that checks BarcodeCache before ever calling Open Food Facts; and Chapter 6 supplies the confirm-and-save form that actually turns the looked-up data into a stored Item with status="active". Remove any one of the three and the step breaks - decoding with nowhere to send the result, a lookup with no scanner to trigger it, or a lookup with no form to save what it found.

EXAMPLE PAIR: STEP 7 (RECIPE SUGGESTION)
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The recipe suggestion depends on Chapter 7 to identify which items are actually expiring soon (the input to the recipe search), and on Chapter 10 to perform the actual TheMealDB fan-out and relevance sort. Chapter 10's own view has nothing meaningful to search for without Chapter 7 first identifying which real ingredients are running low.

WHY THIS WORKS AS AN ANSWER
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It picks two genuinely separate steps and, for each one, names at least two specific earlier chapters whose individual contributions are both necessary - explaining concretely what would break if either contribution were missing, rather than just listing chapter numbers without justification.