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

Perform the multiplication and division from left to right:
14688 ÷ 4992 = 3
3 x 16 = 48
740 x 520 = 384800
309 ÷ 56 = 5.517857142857143
400 ÷ 28 = 14.28571428571429
324 + 20000 = 20324
72 x 800 = 57600
800 ÷ 18 = 44.44444444444444

Perform the addition and subtraction from left to right:

48 + 384800 = 384848
384848 + 5.517857142857143 = 384853.5178571429
384853.5178571429 + 14.28571428571429 = 384867.8035714286
384867.8035714286 + 20324 = 405191.8035714286
405191.8035714286 - 57600 = 347591.8035714286
347591.8035714286 ÷ 44.44444444444444 = 7815

Therefore, the final answer is 7815.