We will have the following:
First, we will have that the total number of outcomes per toss is:
![6\cdot6\cdot6=216](https://img.qammunity.org/2023/formulas/mathematics/college/3v27rohzpv6bxb8p6vphynrga0aga3ke02.png)
Now, the probability of getting a triple is:
![(6)/(216)=(1)/(36)](https://img.qammunity.org/2023/formulas/mathematics/college/pkjgcjuwn7nu81wg79r3fasdtaui3kc9gb.png)
Then, we will have that the probability of not getting a triple is given by:
![(210)/(216)=(35)/(36)](https://img.qammunity.org/2023/formulas/mathematics/college/phufmwyo1qbw7ijthp0u4gau9kwol1yw43.png)
Now, the probability of getting the first win in the third roll is:
![P=(35)/(36)\cdot(35)/(36)\cdot(1)/(36)\Rightarrow P=(1225)/(46656)](https://img.qammunity.org/2023/formulas/mathematics/college/dd12jcxb8wk6yn69snl11f7t2l006r5e1j.png)
![\Rightarrow P\approx0.026](https://img.qammunity.org/2023/formulas/mathematics/college/10hu9hllfqq5tlb5r09eup01wb8mvrt53g.png)
So, the probability is approximately 2.6%.
So, he can expect to roll the dice 35 times before winning.