SATMathematics Practice Test 1

Let x be the original price of the computer, in dollars. The discounted price is 20 percent off the original price, so $\mathit{x}-0.2\mathit{x}=0.8\mathit{x}$ is the discounted price, in dollars. The tax is 8 percent of the discounted price, so $0.08\left(0.8\mathit{x}\right)$ is the tax on the purchase, in dollars. The price p, in dollars, that Alma paid the cashiers is the sum of the discounted price and the tax: $\mathit{p}=0.8\mathit{x}+\left(0.08\right)\left(0.8\mathit{x}\right)$ which can be rewritten as $\mathit{p}=1.08\left(0.8\mathit{x}\right)$.Therefore,the original price, x, of the computer, in dollars, can be written as $\frac{\mathit{P}}{\left(0.8\right)}\left(1.08\right)$ in terms of $\mathit{p}$
Choices A, B, and C are incorrect; each choice either switches the roles of the original price and the amount Alma paid, or incorrectly combines the results of the discount and the tax as 0.8 + 0.08 = 0.88 instead of as $\left(0.8\right)\left(1.08\right)$.