fraction, the numerator and denominator are divided by the same number at the same time (4/5), the original sum of the numerator and denominator is 72, what is the original fraction?
一个分数，分子、分母同时除以一个相同的数得(4/5)，原来分子与分母的和是72，原来的分数是多少？
<gadget id="calculator">4 + 5</gadget>
<output>9</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">72 * (4/9)</gadget>
<output>32</output>

<gadget id="calculator">72 - 32</gadget>
<output>40</output>

<gadget id="calculator">(4/9) / 40</gadget>
<output>1/90 = around 0.011111</output>

<gadget id="calculator">72 * (1/90)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>