A and B have two numbers. After the number A gives 10% of the number B, the two numbers are equal. How much is the original number B less than the number A?
甲乙两数，甲数给乙数10%后，两数相等，原来乙数比甲数少多少
<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">(9/10) - (1/10)</gadget>
<output>4/5 = around 0.8</output>

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

<result>1/5 = around 0.2</result>