The first one is the vertical asymptote found by setting the condition:
6-12x!=06−12x≠0 this is done to avoid a zero in the denominator (that cannot be evaluated) and gives you that must be x!=1/2x≠12
So the vertical line with equation x=1/2x=12 will be an asymptote of your function (cannot be crossed by it).
The horizontal asymptote can be found observing the behaviour of your function for very big values of xx by doing:
lim_(x->oo)((4+3x)/(6-12x)) this will tell you whether or not your function tends to get near to some value.
lim_(x->oo)((4+3x)/(6-12x))=lim_(x->oo)(x(4/x+3))/(6x(1/x-2))=
=lim_(x->oo)(cancel(x)(4/x+3))/(6cancel(x)(1/x-2))=-1/4
So basically your function when x becomes very large tends to become equal to -1/4 so you have a horizontal asymptote (representing the line near which your functions tends) given as:
y=-1/4
Graphically:
graph{(4+3x)/(6-12x) [-10, 10, -5, 5]}