The general form of a line is:
y = mx + b, where m is the slope and b is the y-intercept.
So let's compare the equation you were given with the general form:
y = mx + b (general form)
y = 3/4x - 4 (your equation)
You can see that the m matches up to the 3/4 (so the slope has to be 3/4) and the b matches up to -4, so the y-intercept has to be (0, -4).
Therefore, your final answers are:
y-intercept: (0, -4)
slope: 3/4