China Resources Suguo has a promotion on weekends, 1 liter of milk is 10 yuan per box, buy 3 boxes and get 1 free. Mom bought 3 boxes of this kind of milk at a time, and each box is cheaper than usual.
华润苏果周末促销，1升装牛奶每盒10元，买3盒送1盒，妈妈一次买了3盒这样的牛奶，每盒比平时便宜了多少元．
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">10 * (3/4)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">10 - (15/2)</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>