There's 33.34% chance of being right unless the person happen to know the answer, and lifelines can only get you so far into the game.

Let's say there are 15 questions with 4 choices each. Let's also say there are 3 lifelines: call-a-friend, 50-50, and ask-the-audience.

For each of the 15 questions, there is only 1 correct answer, and 3 incorrect answers, so immediately your chances are 1/3 = 33.34%. You can use each lifeline once. Using phone-a-friend, let's say gives you a 95% chance the person you call is correct. So 1 question is 95%. Similarly, we can say ask-the-audience gives you a 95% chance. Finally, 50-50 will remove 2 wrong answers, so you have 1 right answer and 1 wrong answer, so you basically know the answer. To recap:

Question 1: 33.34%
Question 2: 33.34%
Question 3: 33.34%
Question 4: 95% <--- ask-the-audience
Question 5: 33.34%
Question 6: 33.34%
Question 7: 33.34%
Question 8: 33.34%
Question 9: 95% <--- phone-a-friend
Question 10: 33.34%
Question 11: 33.34%
Question 12: 33.34%
Question 13: 33.34%
Question 14: 33.34%
Question 15: 100% <--- 50-50
Total: 690.08%
Divided by 15 questions = 46.00%
So basically, it's more a less a game of chance, but more than half the people on the show will lose, so it's not very fair. That show is making tons of money off of people.