Repeated Addition: Grocery Shopping Math

In this video, Taco's mom creates a shopping list with prices for various items. Shawnee and Taco help her by adding up the prices of single items and calculating the total cost for items bought in multiples. They use basic addition and multiplication to find the total cost of the shopping list, which is confirmed by their dad.

What method did Taco's mom use to avoid confusion when shopping?

What did Taco's dad confirm about Shawnee and Taco's calculations?