Equation of straight line!

Hey, i need some help with this question!

9(i) Find the gradient of the line *l1 *which has the equation 4x-3y+5=0.

I think its 4 by doing this:

4x-3y+5=0

3y=4x+5

y=mx+c where m is the gradient? Is that right?

(ii) Find an equation of the line *l2* which passes through the point (1,2) and which is perpendicular to the line *l1* giving your answer in the form ax+by+c=0

If someone could give a detailed solution for me, but as simple as possible i would be most grateful!

Thanks very much! :D