The mean of 22.3, 19.7, 25.4 and another number is 23.4. Find the missing number

22.4 im about 58% sure that right

The "mean" is just the arithmetic average.

The average is just the sum of all elements divided by the number of elements.

In this case:

(22.3+19.7+25.4+n) / 4=23.4 combine like terms on left side

(67.4+n) / 4=23.4 multiply both sides by 4

67.4+n=93.6 subtract 67.4 from both sides

n=26.2