9) The price of a shirt is \( \$ 25 \) each. Write an equation that can be used to determine the total cost, \( \$ 100 \), for buying \( s \) shirts. \( \begin{array}{ll}\text { a) } 25+s=100 & \text { b) } 25 s=100 \\ \text { c) } 25-s=100 & \text { d) } \frac{s}{25}=100\end{array} \)

To determine the total cost for buying \( s \) shirts, you'd multiply the number of shirts by the price per shirt. Therefore, the correct equation would be \( 25s = 100 \), indicating that the total cost is the price per shirt multiplied by the number of shirts. In this scenario, if you want to buy shirts for a specific budget, it's crucial to ensure that you don't overspend! A common mistake is forgetting to consider tax or additional fees, which might lead you to accidentally purchase more shirts than your budget allows. Always double-check before heading to the checkout!