1. The problem asks us to write an exponential equation modeling Isabella's weekly sales, where sales increase by 20% each week after the first week. 2. The general form of an exponential growth equation is $$y = a b^x$$ where: - $a$ is the initial amount (sales at week 0), - $b$ is the growth factor per week, - $x$ is the number of weeks after opening. 3. From the problem, the initial sales at week 0 (opening week) is $a = 86$. 4. The sales increase by 20% each week, so the growth factor is $b = 1 + 0.20 = 1.20$. 5. Therefore, the exponential equation modeling the sales is: $$y = 86 (1.20)^x$$ This means each week, sales are multiplied by 1.20 compared to the previous week. Final answer: $$y = 86 (1.20)^x$$