Final answer:
To buy 3 t-shirts after a 40% discount, it will cost $54.
Step-by-step explanation:
To calculate the cost of buying 3 t-shirts after the discount, we need to find the total price of the t-shirts and then apply the discount. Since each t-shirt costs $30, the total cost without the discount would be $30 x 3 = $90.
Now, to calculate the discount, we multiply the total cost by the discount percentage, which is 40%. So, the discount amount is $90 x 40% = $36.
To find the final cost after the discount, we subtract the discount amount from the total cost. Therefore, the cost of buying 3 t-shirts after the discount is $90 - $36 = $54.
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