The average of three numbers is 45. two of the numbers are equal. the last number is 89. what are the two missing numbers?

The average of a set of data is equal to the sum of the values divided by the number of data present. So, if we have three numbers, the average would be:

let x, y and z represent the three numbers
average = x + y + z / 3 = 45

Two number are equal in value, so let x = y. Substituting the value to the expression of average,

45 = x + x + z / 3
45 = 2x + z / 3

It said that the last number is 89 so z is equal to 89.

45 = 2x + 89 / 3
135 = 2x + 89
46 = 2x
x = 23

Therefore, the two numbers are both 23.