Anne bought a computer for $2,000 and then paid a 5 percent sales tax, and Henry bought a computer for $1,800 and then paid a 12 percent sales tax. The total amount that Henry paid, including sales tax, was what percent less than the total amount that Anne paid, including sales tax?

A. 3%
B. 4%
C. 7%
D.10%
E. 12%

The OA is B

Experts, I dont know what are the calculus I should do here. May you show me how to solve this PS question?

Hi Vincen,
Let's take a look at your question.

The price of the computer Anne bought = $2,000
Percentage of Sales tax Anne paid = 5%
Sales tax Anne paid will be:
$$=\ 2,000\times\frac{5}{100}=100$$

Therefore, the total amount Anne paid = 2,000 + 100 = $2,100

The price of the computer Henry bought = $1,800
Percentage of Sales tax Henry paid = 12%
Sales tax Henry paid will be:
$$=\ 1,800\times\frac{12}{100}=216$$

Therefore, the total amount Henry paid = 1,800 + 216 = $2,016

Now we are asked to find the percent decrease of Henry's payment than Anne's Payment.
Percent decrease = [(Anne's Payment - Henry's Payment)/Anne's Payment] * 100%
$$=\ \frac{2100-2016}{2100}\times100\%$$
$$=\ \frac{84}{2100}\times100\%$$
$$=\ \frac{84}{21}\%$$
$$=\ 4\%$$

Hence, the total amount that Henry paid, including sales tax, was 4% less than the total amount that Anne paid, including sales tax.
Therefore, Option B is correct.

Hope it helps.
I am available if you'd like any follow up.