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

This type of question, asked 4 times: 12 Sep 2025 S3, 16 Sep 2025 S1, 16 Sep 2025 S2, 20 Sep 2025 S1. All 4 questions below, oldest first.

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Question 1
12 Sep 2025 S3
16 $If 6 $ 2 = 20 and 4 $ 3 = 19, then 5 $ 2 = ?$
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Question 2
16 Sep 2025 S1
15 $If 3 + 4 = 19 and 2 + 5 = 17, what is 1 + 6 = ?$
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Question 3
16 Sep 2025 S2
22 $If 3 @ 4 = 19, 5 @ 6 = 41, then what is 6 @ 7?$
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Question 4
20 Sep 2025 S1
17 $If 5 @ 2 = 17 and 6 @ 3 = 27, what is 7 @ 4?$
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