The ratio of the length to the width of a rectangle is 7:5, the length is 4 cm longer than the width, what is the width in cm?
长方形的长和宽的比是7：5，长比宽长4厘米，宽是多少厘米．
<gadget id="calculator">7 - 5</gadget>
<output>2</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<result>10</result>