What is happening here?
The puzzle pages (number riddles, magic squares, card targets, dungeon adventures, word problems with an intermediate step) have no fixed method. The child tries, discards, tries again. That is exactly the point: problem solving means finding a way yourself, and that does not work without dead ends.
That is why they are scattered between the practice pages. They are not a test but the part meant to be fun.
What helps at home
Do not give away the solution, even if it is hard. Questions work better: "What do you already know for sure?" "Where could you start?" "What happens if you put the 6 here?"
Set a time window, say ten minutes. After that the puzzle may rest and come back later. It often almost solves itself on the second try, because the brain kept working in the background. Praise the path ("You tried three ideas"), not only the result.
What can go wrong
If the mood tips ("I can't do this"), stopping is better than pushing on. A child who keeps calculating through tears mainly learns that math hurts. Switch to a task that works and come back later.
Taking over too fast is just as wrong. If you calculate and your child watches, it learns that someone else brings the answer. If a puzzle stays too hard for good, that is feedback for us, not about your child. Tell your child that too.