I love this game! I usually play it with my kids on the first day. It’s a great way to assess mental math skills and it’s a great introduction for a conversation on listening skills, auditory verse visual learners, etc. The set of cards I use is one I made, probably 15 years ago. Sarah at Math=Love has a blog post where she compiled a list of cards she found on the Internet. I’m linking it here so I can reference it in the future.