Xiao Ming bought 4 notebooks and 2 fountain pens with 31 yuan. It is known that each fountain pen is 1.5 yuan. How much is each notebook? (column equation solution)
小明用31元钱买了4本笔记本和2支水笔，已知每支水笔1.5元，每本笔记本多少元？(列方程解答)
<gadget id="calculator">2 * 1.5</gadget>
<output>3</output>

<gadget id="calculator">31 - 3</gadget>
<output>28</output>

<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<result>7</result>