If 80 is subtracted from a set of data at the same time, the average of the new data is 2.3, then the average of the original data is?

If 80 is subtracted from a set of data at the same time, the average of the new data is 2.3, then the average of the original data is?

80+2.3=82.3
Subtracting 80 from a set of data is equivalent to subtracting the average of 80

The average value of some five numbers is 20. Change one of them to 40, and the average value is 25. Find this number

5×20=100
5×25=125
125-100 = 25
40- 25 =15
This number is 15

The average of five numbers is 20. If one of them is changed to 40, then the average is 25. The number of changes is 20______ ．

40 - (25 × 5-20 × 5) = 40 - (125-100), = 40-25, = 15