It says b = (-4,-4)? That doesn't make sense. Slope-intercept form is y = mx + b, where b = the y intercept. The y intercept is where x = 0 and it hits the y line. Therefore, the point would be (0, y). So (-4,-4) cannot be b.
I could guess two things. One, it's a typo and you meant (0,-4) which would be the point of the y intercept, but the y intercept (b) actually equals -4, i.e. we'd say b = -4. Or you could mean the point (-4,-4) is a point in the line, but that would not be b. And it will make a big difference.
What I can tell you is that the slope of 3/4 means for every 3 spaces up, you will move 4 spaces to the right. The fraction is "rise over run," or (y1 - y0) / (x1 - x0). That is, the change in y over the change in x.
So 3 is the change in y, and 4 is the change in x. Since the 3 is positive you move up 3 spaces, and since the 4 is positive you move right 4 spaces. And that would be another point.
If we pretend for a minute that (-4,-4) is one point, then moving up 3 gets us to -1, and moving right 4 gets us to 0, so we would be at (0,-1). In this case, the -1 is your y intercept.
But without knowing what you're meaning by b = (-4,-4) there's no way to give a definitive answer to that, only a few basic concepts.