If the numerator of the fraction ((a)/7) is enlarged by 3 times and the denominator is reduced to (1/2), the fraction is (6/7), then what is a equal to?
如果把分数((a)/7)的分子扩大3倍，分母缩小为原来的(1/2)，这个分数是(6/7)，那么a等于多少．
<result>1</result>