To solve this expression, we need to follow the order of operations (PEMDAS).

Step 1: Convert the mixed numbers to improper fractions
5 8\9 = (59 + 8) / 9 = 53/9
3 11\12 = (312 + 11) / 12 = 47/12
7 5\6 = (76 + 5) / 6 = 47/6
15 2\3 = (153 + 2) / 3 = 47/3

Step 2: Perform the operations inside the parentheses
(53/9 - 47/12) 18/71 - 47/6 / 47/3
= (477/108 - 282/108) 18/71 - 47/6 / 47/3
= 195/108 18/71 - 47/6 / 47/3
= 39/216 18/71 - 47/6 / 47/3
= 702/15216 - 47/282 / 47/6
= 702/15216 - 14154/15216 / 2352/15216
= (702 - 14154) / 15216 / 2352/15216
= -13452 / 15216 / 2352/15216
= -13452 / 352128
= -0.0382

Therefore, the answer is approximately -0.0382.