I guess you want to find the 4 numbers
x + x + 2 + x + 4 + x + 6 = -28
4x + 12 = - 28
4x = - 40
x = -10
so the numbers are -10, -8, -6 ,-4.
Add it up then you will get answer
Answer:
x=2.4650
Step-by-step explanation:
I assume that you mean 
so let s use the ln() function

so x = ln(15)/ln(3)
x = 2.4650