Mom went to the supermarket and bought a bag of apples and 3 boxes of milk, which cost a total of 53 yuan. A bag of apples is 17 yuan, how much is a box of milk?
妈妈到超市买了一袋苹果和3盒牛奶，共花了53元．一袋苹果17元，每盒牛奶多少钱？
<gadget id="calculator">53 - 17</gadget>
<output>36</output>

<gadget id="calculator">36 / 3</gadget>
<output>12</output>

<result>12</result>