How do i graph this and is it right?

You seemed to have gotten the equation wrong, but don't worry I'll help you

First you simplify the equation 
4=(-1)(-3)+b
(A negative times a negative is a positive)
4 = 3 + b
(Flip the equation)
b + 3 = 4

Then you subtract 3 from each side
b+3-3=4-3
b = 1 is your answer

y = -1x - 7 is wrong as well
To find the answer just add -4 on each side for y+4=-1(x-3)
y+4+-4=-x+3+-4
y = -x - 1 is the answer
To graph, plot points on Y-intercept of -1 and place another point at (-2,1)