Since the sales tax is added to the selling price, then
The total cost = 3000 + 5.25% of 3000
Let us find 5.25% of 3000
Change the percent to a decimal by divide it by 100
[tex]\frac{5.25}{100}\times3000=157.5[/tex]Then the total cost = 3000 + 157.5
The total cost = 3157.5 dollars