The school originally had 36 football and basketball games, and the ratio of football to basketball was 7:2. After buying some footballs, footballs accounted for 80% of the total. How many more footballs were bought?
学校原有足球和篮球共36个，足球与篮球的比是7：2，又买进一些足球后，足球占总数的80%，又买进足球多少个？
<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">2 / 9</gadget>
<output>2/9 = around 0.222222</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/9) / (1/5)</gadget>
<output>10/9 = around 1.111111</output>

<gadget id="calculator">36 * (10/9)</gadget>
<output>40</output>

<gadget id="calculator">40 - 36</gadget>
<output>4</output>

<result>4</result>