What is an equation of the line slope intercept form that lasses through the given point and has a given slope (8,-8) slope : 3

It is easier to do this in point-slope form first, then convert to slope-intercept later on. 
Point slope equation is (y-y)=m(x-x), where m is the slope, and the second variables of the parenthesis is the point. 
Now we just input the numbers in. 
y+8=3(x-8)
The 8 is positive for the y because it is backwards for these types of equations. 
And then we can distribute the other side. 
y+8=3x-24
Then we subtract 8 from the y to isolate the y. Add the negatives. 
y=3x-32

Hope I helped!