------
## 最终结论
```python
def count_first_elements(t):
    count = 0
    for element in t:
        if isinstance(element, tuple):
            return count
        count += 1

# Test cases
assert count_first_elements((1, 5, 7, (4, 6), 10) ) == 3
assert count_first_elements((2, 9, (5, 7), 11) ) == 2
assert count_first_elements((11, 15, 5, 8, (2, 3), 8) ) == 4
```