Answer:
X=22
Explanation:
This may be confusing but bear with me
20=(x+17+22+18+21)/5 is our equation because
20 is our mean and we are adding all of our values and diving by how many values we have. we have 5 values
we multiply 5 by 20 to cancel the dividing 5 on the right so
100=x+17+22+18+21
To make this simpler we can add all of the values (except x) so
100=x+78
lets subtract 78 from 100
22=x or x=22
I hope this helped