Question 13770
Well, you already have the slope (which is m) so you can plug it right in the equation. 

y=15/-9.6x+b

Then in order to solve for b, you must plug in numbers for b and you have two choices. 
(7.1,-8.3) and (-2.5, 6.7)
You can choose which ever one is easier for you and i'll use (-2.5, 6.7)
As you probably know, -2.5 is the X value and 6.7 is your Y value. 
Then plug them in their places

6.7=15/-9.6(-2.5)+b
To make it easier, -2.5 can be converted into -5/2
6.7=125/32+b
125/32=3.90625
6.7-3.90625=b
b=2.79375
in fraction form, b=447/160

The final answer in slope-intercept form is
y=15/-9.6x+447/160