Question 73809
First, you have to know that given an equation that looks like 
{{{y = m*x + b}}}, the slope is {{{m}}}. The equations that you
are given are all in that form. You can read off the slope in each case.
(a) {{{m = 2}}}
(b) {{{m = 1/2}}}
(c) {{{m = -1/2}}}
(d) {{{m = 1/2}}}
The slopes are all you care about. Forget the {{{b}}}.
Now all you have to know is that if you have 2 lines
and {{{m[1] = m[2]}}}, then the lines are parallel
If {{{m[1] = -(1/m[2])}}}, then the lines are perpendicular
I see right away that (b) and (d) are parallel
And I see that (a) and (c) are perpendicular because
{{{m[1] = -(1/m[2])}}} when {{{m[1] = 2}}} and {{{m[2] = -1/2}}}