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If i have one apple and give you the apple, how many apples do i have?

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.

If i purchase a product for $79.99 and two accessories for 9.99 and 7.00 how much will i owe after taxes applies 8.75%