The numbers x , y , z and w have an average equal to 25. The average of x , y and z is equal to 27. Find w.

Given that the average of (x , y, z and w ) =
25

Then we know that the average = sum of all numbers/ total of
numbers

==> Ave = (x + y + z+w)/4 =
25

==> multiply by 4:

==>
x + y + z + w = 100...........(1)

Also , given the
average of x , y and z is 27

==> Ave = (x+ y+ z) /3 =
27

Multiply by 3:

==> (x+ y+ z)
= 81 ............(2)

We will substitute (2) in
(1):

==> (x + y + z ) + w =
100

==> 81  + w = 100

Now
subtract 81 from both sides:

==> w = 100 -
81

==> w =
19