In the supermarket, 3 bottles of milk and 2 bottles of Coke total 18 yuan, and 3 bottles of Coke and 2 bottles of milk total 17 yuan. So how much is a bottle of milk and a bottle of Coke?
超市里3瓶牛奶、2瓶可乐一共18元，3瓶可乐、2瓶牛奶一共17元．那么一瓶牛奶和一瓶可乐共多少钱？
<gadget id="calculator">18 - 17</gadget>
<output>1</output>

<gadget id="calculator">1 * 3</gadget>
<output>3</output>

<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">3 + 4</gadget>
<output>7</output>

<result>7</result>