Looking at the problem, we need to identify the number that replaces the question mark in the triangular pattern. Each triangle appears to follow a certain rule or mathematical relationship.

Observing Patterns:

1. The numbers in each triangle interact mathematically to produce a consistent relationship across the examples.
2. It’s likely the sum, difference, or a product of the numbers at the vertices leads to the middle or other values.

Let me calculate the rule based on the first few examples:

1. First Triangle (3, 7, 5):

   • $3 + 5 = 7$.

2. Second Triangle (4, 6, 8):

   • $4 + 8 = 6$.

3. Third Triangle (2, 9, 8):

   • $2 + 8 = 9$.

Fourth Triangle:

Given numbers are $2, 7, 3$:

• If we apply the same logic:
  • $2 + 3 = ?$.
  • The missing number is 5.

Answer: (c) 5.

Would you like further clarification or more exploration into the reasoning? Here are some related problems to consider:

1. Can you find alternate patterns in the same triangle setup?
2. How would the solution change if subtraction was applied instead?
3. What happens if a product or ratio is introduced between the numbers?
4. Can this puzzle extend into higher-dimensional geometric figures?
5. What programming logic would solve this type of problem automatically?

Tip: Look for multiple rules in puzzles—they often have alternate solutions!