Hidden rule a @ b = a + b: find it from the examples and apply

This type of question, asked 2 times: 24 Sep 2025 S2, 26 Sep 2025 S3. All 2 questions below, oldest first.

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Question 1
24 Sep 2025 S2
5 $If 4 # 3 = 7, 6 # 2 = 8, then 5 # 7 = ?$
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Question 2
26 Sep 2025 S3
4 $If 9 @ 3 = 12, 5 @ 2 = 7, 8 @ 1 = 9, then 7 @ 4 = ?$
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