Xiaoli's family buys a box of milk and a bag of soy milk every day. Milk costs 2.40 yuan per bag, which is 1.80 yuan more expensive than soybean milk. How much does Xiaoli's family spend on milk and soy milk for a week?
小丽家每天要买一盒牛奶和一袋豆浆．牛奶每袋2.40元，比豆浆贵1.80元．小丽家一个星期买牛奶和豆浆要花多少钱？
<gadget id="calculator">2.4 - 1.8</gadget>
<output>0.6</output>

<gadget id="calculator">2.4 + 0.6</gadget>
<output>3</output>

<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<result>21</result>