Your answer is 26.
We have to go at this kind of backward.
We find the average by adding up the numbers, then dividing by how many numbers we have.
In this example, we will have 5 numbers...so
x divided by 5 = 18
x/5 = 18
x = 90
The sum of all 5 numbers is 90, so then subtract the 4 numbers you already know to find the one you’re missing. (We’ll call it n)
90 - 8 - 12 - 18 - 26 = n
90 - 64 = n
n = 26
Please let me know if you have any questions.