Answer:
The probability that the lead singer's voice isn't working on any given Saturday is 7%.
Now, if she never gets sick for more than 6 consecutive days, and the interval between bouts of illness is inherently unpredictable, we can consider the following scenarios:
1. She is not sick on the upcoming Saturday (probability = 93%).
2. She gets sick in the 1st week and is still sick on the upcoming Saturday (probability = 7%).
3. She gets sick in the 2nd week and is still sick on the upcoming Saturday (probability = 7%).
4. She gets sick in the 3rd week and is still sick on the upcoming Saturday (probability = 7%).
Since these events are mutually exclusive, we can calculate the probability of scenario 1 happening, which is 93%. So, the probability that the lead singer's voice will be fine at the band's next Saturday gig, which is 2 weeks from now, is 93%.