The students planted a batch of saplings, 20% on the first day, 30% on the second day, and 90 more saplings on the second day than on the first day. How many saplings are there in total?
同学们植一批树苗，第一天植了20%，第二天植了30%，第二天比第一天多植90棵，这批树苗一共多少棵？
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(3/10) - (1/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">90 / (1/10)</gadget>
<output>900</output>

<result>900</result>