A fraction reduced to the simplest fraction is (3/7), the sum of the numerator and denominator of the original fraction is 90, what is the original fraction?
一个分数约成最简分数是(3/7)，原分数分子与分母之和是90，原分数是多少？
<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">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">90 * (7/10)</gadget>
<output>63</output>

<gadget id="calculator">(3/10) / 63</gadget>
<output>1/210 = around 0.004762</output>

<gadget id="calculator">90 * (1/210)</gadget>
<output>3/7 = around 0.428571</output>

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