Hi there!
The general equation of a slope-intercept line is :
y = mx + b
Where "m" is the slope and "b" is the y-intercept.
Since your equation is already in the right form, you can easily see that your "m" is equal to -4, which is the slope of the line.
Your answer is: The slope of the line is -4.
There you go! I really hope this helped, if there's anything just let me know! :)