If 4a=2, a+b=2.5, then b=how much.
若4a=2，a+b=2.5，则b=多少．
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2.5 - (1/2)</gadget>
<output>2</output>

<result>2</result>