If 2x+4=9, what is the value of 4x-2.5?
如果2x+4=9，那么4x-2.5的值是多少．
<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(5/2) * 4</gadget>
<output>10</output>

<gadget id="calculator">10 - (5/2)</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>