Factory A has 120 tons of coal, and Factory B has 96 tons of coal. Plant A burns 15 tons of coal per day, and Plant B burns 9 tons of coal per day. After how many days, the tons of coal remaining in the two factories are equal?
甲厂有煤120吨，乙厂有煤96吨．甲厂每天烧煤15吨，乙厂每天烧煤9吨．多少天后，两厂所剩煤的吨数相等？
<gadget id="calculator">120 - 96</gadget>
<output>24</output>

<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<gadget id="calculator">24 / 6</gadget>
<output>4</output>

<result>4</result>