Question 425947
You have essentially solved the problem.
Just solve for b:
Your 4th step has -10 = -8/3 + b -> b = -10 + 8/3 = -30/3 + 8/3 = -22/3
So the function is 
f(x) = (-4/3)x - 22/3
The graph looks like this:
{{{graph(300,200,-10,10,-10,10,(-4/3)x - 22/3)}}}