A brine, the content of salt accounts for (1/10) of brine. This salt water contains 90 kg of water, how many kg of salt.
一种盐水，盐的含量占盐水的(1/10)．这种盐水含水90千克，含盐多少千克．
<gadget id="calculator">1 / 10</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">90 / (9/10)</gadget>
<output>100</output>

<gadget id="calculator">100 - 90</gadget>
<output>10</output>

<result>10</result>