The sum of the numerator and denominator of a fraction is 90. If 10 is added to the numerator, the fraction is equal to 1. What is the fraction?
一个分数的分子与分母的和是90，如果分子上加10，这个分数就等于1，则这个分数是多少．
<gadget id="calculator">90 - 10</gadget>
<output>80</output>

<gadget id="calculator">1 + 1</gadget>
<output>2</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">80 / 2 / 50</gadget>
<output>4/5 = around 0.8</output>

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