6 - [5/6 + {3 7/8 - 2 1/3 + 1 7/9}] = _____________?

A. 3 9/13
B. 1 9/11
C. 2 11/72
D. None of these

Explanation:

6 – [5/6 + {3 7/8 – 2 1/3} + 1 7/9] => 6 – [5/6 + {3 1/8 – 7/3} + 16/9]

=> 6 – [5/6 + {(279 – 168 + 128)/72}] => 6 – 5/6 + 239/72
=> 6 – (60 + 239)/72 => 6 – 46 – 11/72
=> 2 – 11/72 => 1 + 1 – 11/72 => 1 + 61/72 = 1 61/72

6 – [5/6 + {3 7/8 – 2 1/3 + 1 7/9}] = _____________?