What natural number is filled in () below, the inequality holds? 5 / 9

What natural number is filled in () below, the inequality holds? 5 / 9

The reciprocal of 5 / 9 is 9 / 5
The reciprocal of 9 / () is () / 9
The reciprocal of 1 is 1
Because 5 / 91
That is 81 / 45 > 5 * () / 45 > 45 / 45
81 > 5 * () > 45
The natural numbers of () days are 10,11,12,13,14,15,16