Please translate to English so that I can help
The algebraic expression would be 4 - n, I believe.
First, and most important, you must know what the question is. You haven't told us what the question is, and a gray cloud hangs like a dark mist over the problem, giving the unmistakable impression that you're not too sure of it yourself.
X+4x=35-20. 5x=35-20. 5x=15. X=3