Step 1: Convert mixed numbers to improper fractions

2 13/48 = (2 48 + 13) / 48 = 109 / 48
2 2/15 = (2 15 + 2) / 15 = 32 / 15
3 3/4 = (3 4 + 3) / 4 = 15 / 4
9 3/4 = (9 4 + 3) / 4 = 39 / 4

Step 2: Perform addition and subtraction

(109 / 48 + 32 / 15) / (15 / 4 - 39 / 4) : 12
= (109 15 + 32 48) / (48 15) / (15 - 39) : 12
= (1635 + 1536) / 720 / -24 : 12
= 3171 / 720 / -24 : 12
= (3171 / 720) / -12
= 3171 / 720 / -12
= (3171 / 720) (1 / -12)
= 3171 / -864

So, the final result is 3171 / -864.