The sum of the numerator and denominator of a fraction is 84, and it is reduced to the simplest fraction (2/5). So, what is the numerator of this fraction?
一个分数的分子和分母的和是84，把它化成最简分数是(2/5)．那么，这个分数的分子是多少？
<gadget id="calculator">2 + 5</gadget>
<output>7</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">84 * (2/7)</gadget>
<output>24</output>

<result>24</result>