The symbol (x) represents the largest integer not greater than x, such as (5)=5, (6.31)=6. If (((3x+7)/7))=4, how many such positive integers x are there?
符号(x)表示不大于x的最大整数，例如(5)=5、(6.31)=6．如果(((3x+7)/7))=4，这样的正整数x有多少个．
<result>3</result>