I will try this one.
There are 3 cases to consider:
1) He rolls a sum of 3 on the first turn
2) He rolls a sum greater than 3 on the first turn, and then he rolls a sum of 3
3) He rolls a sum of 2 that get him to 99 and then he rolls a sum of 4
P(1)
He rolls: (2,1) or (1,2), meaning the probability is 2/36.
P(2)
The first roll of getting a number greater than 3: 11/12. Second roll of rolling a 3: 1/18 This means the total probability is 11/12 x 1/18 = 11/216
P(3)
The probabilty of getting a 2 to get to 99: 1/36. The probability of getting a 4: 1/12. This means that teh total propbabilty is 1/36 x 1/12 = 1/432
Add em all up, and you find the total probability is \(\color{brown}\boxed{47\over 432}\)