Which of the following is an example of an equation with exactly one solution?

To determine which of the given equations has exactly one solution, we can analyze each option:

1. **3x + 4 = 3x + 3**
Subtracting \(3x\) from both sides gives:
\(4 = 3\)
This is a false statement, so it has no solutions.

2. **3x + 4 = 3x + 4**
Subtracting \(3x + 4\) from both sides gives:
\(0 = 0\)
This is always true, so it has infinitely many solutions.

3. **4x + 3 = 4x + 3**
Similar to the previous one, subtracting \(4x + 3\) from both sides gives:
\(0 = 0\)
This also is always true, so it has infinitely many solutions.

4. **3x + 4 = 4x + 3**
Subtracting \(3x\) from both sides gives:
\(4 = x + 3\)
Subtracting 3 from both sides results in:
\(x = 1\)
This equation has exactly one solution, \(x = 1\).

The equation with exactly one solution is:
**3x + 4 = 4x + 3**.