the chart below shows one stores sales of computers, listed by model.\nmay\njune\nif the changes in sales…

Explanation:

Step1: Calculate total sales in May

$262 + 282+223 + 135+148=1050$

Step2: Calculate total sales in June

$173+184 + 148+153+212 = 870$

Step3: Calculate the percent - change from May to June

Percent change formula is $\frac{\text{New}-\text{Old}}{\text{Old}}\times100%$. Here, $\text{Old}=1050$, $\text{New}=870$. So the percent change from May to June is $\frac{870 - 1050}{1050}\times100%=\frac{- 180}{1050}\times100%\approx - 17.14%$

Step4: Assume the same percent - change from June to July

Let the total sales in July be $x$. We know that $\frac{x - 870}{870}\times100%=-17.14%$. Then $x-870=870\times(- 0.1714)$. So $x = 870\times(1 - 0.1714)=870\times0.8286 = 721.8$ The percent change from June to July using the formula $\frac{\text{New}-\text{Old}}{\text{Old}}\times100%$ with $\text{Old}=870$ and $\text{New}=721.8$ is $\frac{721.8 - 870}{870}\times100%=\frac{-148.2}{870}\times100%\approx - 17.1%$

Answer:

a. $17.1%$