Adding parentheses means that the equation holds. 90-54/9-6=12．
添上小括号，是等式成立．90-54/9-6=12．
<gadget id="calculator">90 - 54</gadget>
<output>36</output>

<gadget id="calculator">9 - 6</gadget>
<output>3</output>

<gadget id="calculator">36 / 3</gadget>
<output>12</output>

<result>12</result>