If the numerator of the fraction ((a)/7) is enlarged by 3 times, the fraction is equal to 2(1/7), then a=how much.
如果把分数((a)/7)的分子扩大3倍，这个分数等于2(1/7)，那么a=多少．
<gadget id="calculator">15 / 7</gadget>
<output>15/7 = around 2.142857</output>

<gadget id="calculator">(15/7) * 7</gadget>
<output>15</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<result>5</result>