1. The problem is to find the average (mean) of the given numbers: 89, 77, 79, 71, 65, 71, 67, 67, 76, 92, 40, 74, 79, 66, 53, 75, 83, 50, 67, 66, 65, 74, 80. 2. The formula for the average of $n$ numbers $x_1, x_2, ..., x_n$ is: $$\text{Average} = \frac{x_1 + x_2 + ... + x_n}{n}$$ 3. Count the total numbers: there are 23 numbers. 4. Sum all the numbers: $$89 + 77 + 79 + 71 + 65 + 71 + 67 + 67 + 76 + 92 + 40 + 74 + 79 + 66 + 53 + 75 + 83 + 50 + 67 + 66 + 65 + 74 + 80 = 1617$$ 5. Calculate the average: $$\frac{1617}{23} = 70.3043478261 \approx 70.30$$ 6. Therefore, the average of the given numbers is approximately 70.30.