For a fraction, the sum of its numerator and denominator is 80, and the ratio of numerator to denominator is 3:7. Find this fraction?
一个分数，它的分子和分母的和是80，分子和分母的比是3：7，求这个分数？
<gadget id="calculator">3 + 7</gadget>
<output>10</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">80 * (3/10)</gadget>
<output>24</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">80 * (7/10)</gadget>
<output>56</output>

<gadget id="calculator">24 / 56</gadget>
<output>3/7 = around 0.428571</output>

<result>3/7 = around 0.428571</result>