Zhaozhuang's militiamen swam across a big river with arms, and it took (5/7) hours for the first time, and (7/9) hours for the second time, which time was faster? How many hours sooner?
赵庄民兵连武装泅渡一条大河，第一次用(5/7)小时，第二次用(7/9)小时，那一次快些？快多少小时？
<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>

<result>4/63 = around 0.063492</result>