Final answer:
The correct price for the third main dish to achieve an average price of $11 for all three dishes would be $9, which is not listed in the given options. The student likely made a calculation error since option c) $9.75 is not correct.
Step-by-step explanation:
The question involves finding the price for the third main dish of a cafe such that the average price of the three dishes is $11. To solve this, we can use the formula for the average of three numbers, which is the sum of the three numbers divided by three. Since we already have two dish prices, we can calculate the combined total of those two and then determine what the third dish price needs to be to reach the desired average.
Total price for all three dishes to achieve an average of $11: 3 dishes × $11/dish = $33.
If one dish is $15.40 and the second is $8.60, their total is $15.40 + $8.60 = $24.
The price of the third main dish needs to be $33 (total desired) - $24 (sum of the first two dishes) = $9.
Therefore, option (c) $9.75 is not correct. The student might have made a mistake in the calculation, as the correct answer should be $9, which is not listed in the options provided. In a real-world scenario, the cafe owner might round to a nearby attractive pricing point, such as $8.95 or $9.00.