Final answer:
The probability of at least one engine not firing is 8.73%.
Step-by-step explanation:
To find the probability of at least one engine not firing, we can use the complement rule. The probability of at least one engine not firing is equal to 1 minus the probability that all three engines fire.
Since the engines are independent, the probability that all three engines fire is equal to the product of their individual probabilities of firing. So, the probability of at least one engine not firing is 1 - (0.97 * 0.97 * 0.97). This simplifies to 1 - 0.912673, which is approximately 0.087327, or 8.73%.