After the holiday season, the average number of costumers per day at the game galaxy store decreased from 612 to 450. find the percent of decrease

Simple, finding markdown, use these two formulas.

Markdown=Original-New
and
Percent Markdown= Markdown Amount/Original*100

So,

Markdown=612-450
M=162

Markdown%= 162/612*100
M%=0.2647*100
M%=26.5 (rounded)

Thus, there was a 26.5% decrease.

We need more info then that