A school recently planted some trees, but 20 did not survive, and the survival rate was 80%. How many trees were planted in the school?
某学校最近植了一些树，20棵没有成活，成活率为80%，学校共植了多少棵树？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">20 / (1/5)</gadget>
<output>100</output>

<result>100</result>