In order to better implement sports activities, a school in Hubei plans to import a batch of basketballs and footballs in the new semester. There are 15 more basketballs than footballs, and the price of basketballs is 20% higher than that of footballs. If a shopping mall receives this business, buys these basketballs and footballs for 2400 yuan, sells the footballs at a unit price of 20 yuan, and sells these balls for a total profit of 820 yuan, how many footballs did the school buy?
湖北某学校为了更好地落实体育活动，新学期准备进一批篮球和足球，篮球比足球多15个，且篮球价格比足球高20%．若某商场接到这笔生意后，用2400元买进这批篮球和足球，出售足球的单价为20元，售出这批球共获利润820元，求学校买了多少个足球？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">20 * (6/5) * 15</gadget>
<output>360</output>

<gadget id="calculator">820 - 360</gadget>
<output>460</output>

<gadget id="calculator">2_400 + 460</gadget>
<output>2_860</output>

<gadget id="calculator">20 * (6/5)</gadget>
<output>24</output>

<gadget id="calculator">20 + 24</gadget>
<output>44</output>

<gadget id="calculator">2_860 / 44</gadget>
<output>65</output>

<result>65</result>