Question

three of the four numbers have a sum of 22. Th average of the four numbers is 4. what is the fourth number

Answer 1

Let the unknown number be x.
Then we can write:
\[\large \frac{22+x}{4}=4\ .......(1)\]
Now just solve (1) to find x.

Answer 2

Three of four numbers have a sum of 22.
a + b + c = 22
:
If the average of the four numbers is 4,
a+b+c+d/4= 4

Replace a + b + c with 22
22+d/4= 4
multiply both sides by 4
22 + d = 16
d = 16 - 22
d = -6 is the fourth number