Answer:
Part 1) 
Part 2) The graph in the attached figure
Step-by-step explanation:
Part 1)
we know that
The linear equation in slope intercept form is equal to

where
m is the slope
b is the y-intercept
we have

substitute in the linear equation

solve for b

substitute

Part 2) Draw the equation
we know that
To graph a line we need two points
we have the y-intercept (0,4) and (2,-4)
Plot the points, connect them and join to draw the line
see the attached figure
You simply put 40 over a hundred and 55 over n (which is the number were trying to find) so you do cross multiplication. 55 times a hundred and after you get the answer. You divide it by 40 and should get 137.5.
63.5 if u want working out let me know