Answer :
We will have the following:
First, we will have that the total number of outcomes per toss is:
[tex]6\cdot6\cdot6=216[/tex]Now, the probability of getting a triple is:
[tex]\frac{6}{216}=\frac{1}{36}[/tex]Then, we will have that the probability of not getting a triple is given by:
[tex]\frac{210}{216}=\frac{35}{36}[/tex]Now, the probability of getting the first win in the third roll is:
[tex]P=\frac{35}{36}\cdot\frac{35}{36}\cdot\frac{1}{36}\Rightarrow P=\frac{1225}{46656}[/tex][tex]\Rightarrow P\approx0.026[/tex]So, the probability is approximately 2.6%.
So, he can expect to roll the dice 35 times before winning.