Let's consider two prime numbers, 3 and 5. The sum of these prime numbers is 3 + 5 = 8, which is a composite number.
The divisibility rule that proves the sum of 3 and 5 is composite is the divisibility rule for 2. According to this rule, a number is divisible by 2 if it ends in an even digit (0, 2, 4, 6, or 8).
In the case of the sum 3 + 5 = 8, we can see that 8 is divisible by 2 because it ends in an even digit (8). Therefore, following the divisibility rule for 2, we can conclude that the sum of 3 and 5 (8) is a composite number.
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