First, let's put that line in standard form
y - 3 = 3(x + 1)
y - 3 = 3x + 3
y = 3x + 6
(Standard form is y = mx+b, where m is slope and b is y-intercept.)
Now, a line parallel to that line would have the same slope of 3. So now we have m = 3. Plug that in for m and now we have
y = 3x + b
But we still need the b value. We can get that by plugging in the point (0, -3)
(-3) = 3(0) + b
-3 = 0 + b
b = -3
Now put b back into the equation and your final equation is
y = 3x - 3
