In the long history of the earth, 90,900 species of birds have died out, 900 species more than 10 times the number of birds now. How many species of birds are there? (solution by equation)
在地球漫长的历史上，已经有90900种鸟类消亡，比现在鸟类的10倍还多900种．现存鸟类多少种？(用方程解)
<gadget id="calculator">90_900 - 900</gadget>
<output>90_000</output>

<gadget id="calculator">90_000 / 10</gadget>
<output>9_000</output>

<result>9_000</result>