The original ratio of coffee and milk powder in the supermarket is 5:7, after purchasing 40 boxes of coffee today. The quantity ratio of coffee and milk powder has changed to 7:9, how many boxes of coffee are there now?
超市原有的咖啡和奶粉数量比为5：7，今天进货40箱咖啡后．咖啡和奶粉的数量比变为7：9，问现在的咖啡有多少箱？
<gadget id="calculator">7 / 9</gadget>
<output>7/9 = around 0.777778</output>

<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(7/9) - (5/7)</gadget>
<output>4/63 = around 0.063492</output>

<gadget id="calculator">40 / (4/63)</gadget>
<output>630</output>

<gadget id="calculator">630 * (7/9)</gadget>
<output>490</output>

<result>490</result>