In all versions, students must engage basic addition and subtraction facts. In the memory version, after a student has turned over one card, in order to know whether there is a match using cards they've seen, they need to to solve equations of the given form. Students could also be asked to record the number sentences they make, either with available 'symbol' cards as envisioned in the hypothetical picture above, or on paper or white board to reinforce written work and allow the teacher to evaluate whether students are making all possible kinds of number sentences.