The school planted 500 trees in spring, with a survival rate of 85%, and the survival rate of tree planting in autumn was 90%. It is known that 20 more trees died in spring than in autumn. How many trees to plant in fall?
学校春季植树500棵，成活率85%，秋季植树的成活率是90%．已知春季比秋季多死了20棵树．秋季植树多少棵？
<gadget id="calculator">85 / 100</gadget>
<output>17/20 = around 0.85</output>

<gadget id="calculator">500 * (17/20)</gadget>
<output>425</output>

<gadget id="calculator">500 - 425</gadget>
<output>75</output>

<gadget id="calculator">75 - 20</gadget>
<output>55</output>

<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">55 / (1/10)</gadget>
<output>550</output>

<result>550</result>