Question 956799
(1):

{{{3x-4y=3*(-8)-4*(-5)}}}



(2):


{{{5x-2y=5*6-2*4}}}



Those are given in their unsimplified form so you can understand how working with standard form equation of a line can be handled.  Also be aware or reminded, a line parallel to another will have the same slope as it.  The slopes of two lines perpendicular in a plane are negative reciprocals of each other.


MORE:
Understanding how standard form works is necessary.
{{{Ax+By=C}}}, standard form for a line.
{{{By=-Ax+C}}}
{{{y=-(A/B)x+C/A}}}, slope-intercept form for a line.
The slope is {{{-(A/B)}}}.  Any line in the plane parallel will have slope {{{-A/B}}}, and any line perpendicular will have slope  {{{B/A}}}.
-
The rest of the work would be straightforward.