Wang Qing bought 4 notebooks and 6 ballpoint pens, and the total cost was 22.4 yuan. 1.9 yuan per ballpoint pen, how much is each notebook? (solution by equation)
王青买了4本笔记本和6枝圆珠笔，共用去22.4元．每枝圆珠笔1.9元，每本笔记本多少钱？(用方程解)
<gadget id="calculator">1.9 * 6</gadget>
<output>11.4</output>

<gadget id="calculator">22.4 - 11.4</gadget>
<output>11</output>

<gadget id="calculator">11 / 4</gadget>
<output>11/4 = around 2.75</output>

<result>11/4 = around 2.75</result>