Slope intercept form is y = ax + b, where a is equal to the slope value, and b is equal to the y-intercept.
You have both the slope and y-intercept, which means that all you need to do is plug in the numbers to the equation in order to get your answer!
Let's plug in -7 for a, which gives you y = -7x + b.
Next, we'll plug in the y-intercept, which gives you y = -7x + 9.
Hope this helps!! :)