Let's translate this question into a formula:
Total cost = (unit price of the eraser) (number of erasers purchased)
Final total cost = (Total cost) * 1.08 = ?
Why? The Final Total Cost = Cost of the erasers + (Cost of the erasers)(sales tax rate)
Final total cost = 1.08 (Total Cost)
Final total cost = 1.08 ($0.50)(24) (since 1 dozen = 12, and 2 dozen = 24)