The number of A is 20, first decrease by 10%, and then increase by 10%, what is the number of A now?
甲数是20，先减少10%，再增加10%，现在的甲数是多少？
<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

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

<gadget id="calculator">1 + (1/10)</gadget>
<output>11/10 = around 1.1</output>

<gadget id="calculator">20 * (9/10) * (11/10)</gadget>
<output>99/5 = around 19.8</output>

<result>99/5 = around 19.8</result>