Final answer:
The price of the pizza in 1964 was $2.31.
Step-by-step explanation:
To find the price of the pizza in 1964, we need to first calculate the discount amount. The pizza was marked down by 85%, so the discount is 85% of $15.40. To calculate the discount, multiply $15.40 by 0.85:
Discount = $15.40 x 0.85 = $13.09
The discounted price of the pizza is $15.40 - $13.09 = $2.31. Therefore, the price of the pizza in 1964 was $2.31.