In a set of seven numbers the average of the first four is 15 and the average in the last three is 8 then what is the average in all 7?

To find the average of all seven numbers, we can use the formula for the average: (sum of all numbers) / (total number of numbers). Given that the average of the first four numbers is 15, the sum of the first four numbers is 15 * 4 = 60. Similarly, the sum of the last three numbers is 8 * 3 = 24. Therefore, the sum of all seven numbers is 60 + 24 = 84. Finally, the average of all seven numbers is 84 / 7 = 12.