Row of N: A is p-th from left, B is q-th from right: how many between them

The same question, asked 3 times: 12 Sep 2025 S2*, 14 Sep 2025 S1*, 15 Sep 2025 S3. Every wording below, oldest first.

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Question 1
12 Sep 2025 S2
13 $In a row of 50 books, Book A is 15th from left and Book B is 20th from right. How many books lie between them?$
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Question 2
14 Sep 2025 S1
14 $There are 40 students in a line. Rahul is 13th from the left and Kunal is 17th from the right. How many students are there between them?$
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Question 3
15 Sep 2025 S3
14 $In a row of 60 students, Meena is 25th from the left and Rupa is 20th from the right. How many students are there between them?$
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Question 1