Final answer:
To find the cost of each poster, divide the total cost by the number of posters. In this case, each poster costs $9.75.
Step-by-step explanation:
To find the cost of each poster, you need to divide the total cost by the number of posters. In this case, you bought 8 posters and the total cost is $78. To find the cost of each poster, divide 78 by 8.
Cost per poster = $78 / 8 = $9.75.
Therefore, each poster costs $9.75.