Answer
Step-by-step explanation
The mean is the sum of variables divided by the number of variables
Mean = (Σx)/N
x = each variable
Σx = Sum of the variables
N = number of variables
Let the fourth number be a
Σx = Sum of the variables = a + 80 + 95 + 85 = a + 260
N = number of variables = 4
Mean = 88