The school planted 200 trees for afforestation, but 20 of them did not survive. Find the survival rate.
学校造林绿化，栽下了200棵树，结果有20棵没成活．求成活率．
<gadget id="calculator">200 - 20</gadget>
<output>180</output>

<gadget id="calculator">180 / 200</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(9/10) * 1</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>