Players probabilities of winning are 4/7 , 2/7, 1/7 which of course sum to 1.
Step-by-step explanation:
The coin theoretically could give a very large number of tails first so each person's probability is made up of an infinite series.
P(1st person wins) = P(H) + P(TTTH) + P(H) + . . . etc
= 1/2 + (1/2)^4 + (1/2)^7 + (1/2)^10 + . . .
This is a geometric series with first term a = 1/2 and common ratio r = 1/8
Using formula a/(1 - r) this is (1/2)/(7/8) = 4/7
P(2nd person wins) = P(TH) + P(H) + P(H)
= (1/2)^2 + (1/2)^5 + (1/2)^8 + . . .
Geometric series with sum (1/4)/(7/8) = 2/7
P(3rd person wins) = P(TTH) + P(H) + P(H) + . . .
= (1/2)^3 + (1/2)^6 + (1/2)^9 + . . .
Geometric series with sum (1/8)/(7/8) = 1/7
Players probabilities of winning are 4/7 , 2/7, 1/7 which of course sum to 1.
Hope this helped!