Hi there!
FACTS :
The general form of a y-intercept equation is : y = mx + b
Where "m" is the slope of the line and "b" is the y-intercept.
STEPS TO ANSWER:
You want the same slope as this equation : y = 9 - 9x
This equation is the same as : y = -9x + 9
In this equation the slope is : -9
You want the same y-intercept as this equation : y = -10x - 9
In this equation the y-intercept is : -9
Your slope is -9 and your y-intercept is also -9.
This means that the equation of your new line would look like this :
y = -9x - 9
There you go! I really hope this helped, if there's anything just let me know! :)