Original total = 10 × 76 = 760.<br><br>
Let r = number of exams retaken.<br>
Total increase from retakes = 8 × r.<br>
New total = 760 + 8r.<br><br>
New average = (760 + 8r) ÷ 10 = 78.4.<br>
760 + 8r = 784.<br>
8r = 24, so r = 3.<br><br>
Final Answer: 3