1. **Problem:** Use all 7 cards (2, 4, 1, 3, +, ×) to complete the calculation: $(__ + __) \times __ = 9$. 2. **Formula and rules:** The expression is of the form $(a + b) \times c = 9$ where $a$, $b$, and $c$ are numbers from the cards 2, 4, 1, 3. 3. **Step-by-step solution:** - Try combinations of $a$ and $b$ such that $a + b$ is a factor of 9. - Factors of 9 are 1, 3, and 9. - Possible sums $a + b$ from cards: - $2 + 1 = 3$ - $4 + 1 = 5$ - $3 + 1 = 4$ - $2 + 3 = 5$ - $4 + 3 = 7$ - $2 + 4 = 6$ - Only $2 + 1 = 3$ matches a factor of 9. - Then $c = \frac{9}{3} = 3$. - Check if $c=3$ is in the cards and unused: yes. - So the expression is $(2 + 1) \times 3 = 9$. 4. **Final answer:** $$(2 + 1) \times 3 = 9$$ q_count is 5 because there are 5 distinct problems in the user message, but only the first is solved here.