If the sales tax rate is 8%, which proportion can be used to find the amount of sales tax x, in dollars, for headphones priced at $17.99?

The correct proportion for finding the amount of sales tax, x, for headphones priced at $17.99 with a sales tax rate of 8% is established by relating the percentage to the total price.

In this case, the sales tax rate (8%) represents a part of the total price (the amount of sales tax is a part of the total price). The proportion compares the percentage of tax (8%) to the whole (100%) as it relates to the amount of tax (x) being applied to the total price of the headphones ($17.99).

This is represented mathematically as (8/100) = (x/17.99), where 8 represents the sales tax percentage, 100 represents the whole amount (in percentage terms), x is the unknown amount of tax, and 17.99 is the price of the headphones. This proportion sets up a clear relationship that allows us to solve for x, making it a valid and effective way to determine the sales tax.

Using this relationship, one can cross-multiply and solve for the value of x, allowing for straightforward calculation of the sales tax on the item.