There are 40 red and black balls, and the red balls are 2/3 of the black balls. How many fewer red balls are there than the black balls?
红黑球共40个，红球是黑球的(2/3)，红球比黑球少多少个？
<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">40 * (1/5)</gadget>
<output>8</output>

<result>8</result>