The ratio of the number of boys to girls participating in a mathematics competition in a certain school is 6:5, and 5 girls are added later. At this time, the number of girls is equal to the number of boys (8/9). How many girls originally participated in the math competition?
某校参加数学竞赛的男生与女生的人数比是6：5，后来又增加了5名女生，这时女生人数是男生人数的(8/9)．原来参加数学竞赛的女生有多少人？
<gadget id="calculator">8 / 9</gadget>
<output>8/9 = around 0.888889</output>

<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">(8/9) - (5/6)</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">5 / (1/18)</gadget>
<output>90</output>

<gadget id="calculator">90 * (5/6)</gadget>
<output>75</output>

<result>75</result>