What is the value of f(x) = 3x^2 + 2x - 5 when x = 4?
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Math Question: What is the value of 'y' in the linear function f(x) = x when x = 5?
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Math Question: The original price of a shirt was $40. If Mark buys it on sale for 20% off and then pays a 6% sales tax, what is the final price he pays?