7(x-1.2)=2.1.
7(x-1.2)=2.1．
<gadget id="calculator">7 * 1.2</gadget>
<output>8.4</output>

<gadget id="calculator">8.4 + 2.1</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 / 7</gadget>
<output>1.5</output>

<result>1.5</result>