If 1.5x+3=4.5, then 2x-0.9=how much.
若1.5x+3=4.5，则2x-0.9=多少．
<gadget id="calculator">4.5 - 3</gadget>
<output>1.5</output>

<gadget id="calculator">1.5 / 1.5</gadget>
<output>1</output>

<gadget id="calculator">2 * 1</gadget>
<output>2</output>

<gadget id="calculator">2 - 0.9</gadget>
<output>1.1</output>

<result>1.1</result>