Solve two-step word problems, choosing operations and checking that the answer makes sense.
Real problems often take two steps. Read carefully, figure out what happens FIRST, solve that, then use your result for the second step. Underline the numbers and the question.
After you get an answer, ask "does this make sense?" If a question asks how many are LEFT and your answer is bigger than you started with, something went wrong.
Mastery looks like: They plan and solve two-step problems, label both steps, and sense-check the result.
Common stumbles: Doing only one step; grabbing numbers without deciding the operation; skipping the sense-check.