Subtract 0.7 from 7.8, subtract 4 times in a row, what is the result?
7.8减去0.7，连续减4次，结果是多少．
<gadget id="calculator">0.7 * 4</gadget>
<output>2.8</output>

<gadget id="calculator">7.8 - 2.8</gadget>
<output>5</output>

<result>5</result>