When x=how much, the left and right sides of 2x+0.5x=17.5 are equal.
x=多少时，2x+0.5x=17.5的左右两边相等．
<gadget id="calculator">2 + 0.5</gadget>
<output>2.5</output>

<gadget id="calculator">17.5 / 2.5</gadget>
<output>7</output>

<result>7</result>