set 1. The average of the first three numbers was 42 . The average of the next seven numbery 59 was only 12 . What was the average of all ten numbers?

To find the average of all ten numbers, we need to calculate the total sums of the groups of numbers. For the first three numbers with an average of 42, the total sum is: \( 3 \times 42 = 126 \). For the next seven numbers with an average of 12, the total sum is: \( 7 \times 12 = 84 \). Now, we'll add both sums together: \( 126 + 84 = 210 \). Now, we can find the average of all ten numbers: \( \text{Average} = \frac{\text{Total Sum}}{\text{Number of Items}} = \frac{210}{10} = 21 \). So, the average of all ten numbers is 21.