Let's calculate how much for the $12 t - shirt after the discount.
First, convert 40% into a decimal,

Next, multiply the cost by the discount,

Lastly, subtract the amount discounted,

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Now
Let's calculate the amount after the sales tax,
First convert 9% to a decimal,

Next, multiply the cost of the t - shirt by the sales tax,

Lastly, add the amount of sales tax to the price of the t - shirt,

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Answer : the t - shirt will be $7.90 after everything.
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I hope that helps you out!!!
Any more questions, please feel free to ask me and I will gladly help you out!!!
~Zoey