420.5-294/2.8*2.1．
420.5-294/2.8*2.1．
<gadget id="calculator">294 / 2.8</gadget>
<output>105</output>

<gadget id="calculator">105 * 2.1</gadget>
<output>220.5</output>

<gadget id="calculator">420.5 - 220.5</gadget>
<output>200</output>

<result>200</result>