Let the equation of required line having intercepts a and b with the axes is x/a+y/b=1.

Now, according to given information, P is the mid-point of AB
Therefore, P = (a/2,b/2) => (-3,4). Then (a,b) will be (-6,8).

So, the equation is 4x-3y+24=0. (By substituting in the above equation)