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

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

133 degrees

Step-by-step explanation: