一家商店正在进行促销活动。

它不会直接告诉你答案，而是问你卡在哪一步看看 AI 是怎么陪你一步步弄懂这道题的

完整解法

1. Find the total cost of the dress and shirt before the discount.

Cost of dress = $3y$
Cost of shirt = $y$
Total cost before discount = $3y + y = 4y$

2. Apply the discount for buying 2 items.

Discount for 2 items = $\char36{}5$
Total amount paid = $4y - 5$

答案

$(4y - 5)$

1. Form an expression for the total cost of the three items before the discount.

Total cost before discount = $3y + y + (y + 20) = 5y + 20$

2. Apply the discount and set up an equation for the total amount paid.

Since she bought 3 items, she gets a $10 discount.
Total paid = $(5y + 20) - 10 = 5y + 10$
$5y + 10 = 140$

3. Solve the equation for $y$.

$5y = 140 - 10$
$5y = 130$
$y = \frac{130}{5} = 26$

答案

$26$

AI 分析，可能出错

用 AI 批改，圈出写错的那一步，并自动将你的薄弱点存入错题本，形成你的错因库。