Solve the equation: (9+x)*2=28.
解方程：(9+x)*2=28．
<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<gadget id="calculator">28 - 18</gadget>
<output>10</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<result>5</result>