Answer:
n=19
Explanation:
To solve, we need to get n by itself. 
First, move all the numbers to one side of the equation 
4-n=-15 
Subtract 4 from both sides 
4-4-n= -15-4 
-n=-19
Now all the numbers are on one side, and the variables are on the other. n is still not by itself, or is being multiplied by -1. To undo this, divide both sides by -1. 
-n/-1=-19/-1
n=19