Multiply the cost of an item or service by the sales tax in order to find out the total cost.<span>Make sure you put the sales tax into decimal form. You do this by taking the percentage and sliding the decimal point two places to the left: ...<span>Example: $60 (item cost) x .075 (sales tax) = $4.5 total sales tax.</span></span>
Cross multiplying we get
x^2 = 2*7x
x^2 = 14x
x^2 - 14x = 0 is the answer
