The mean of a set of data is 45 years. find the missing numbers in the data set {40, 45, 48, ? , 54, ? , 45}. explain the method or strategy you used.

There are 7 numbers.  7 X 45 equals 315.  40+45+48+54+45=232.
315-232=83.

The 2 numbers can each have different values, such as 41 and 42, or 40 and 43.  The numbers must add up to 83, though.