Step-by-step explanation:
the slope is always the factor of x.
it is expressed as ratio y/x indicating how many units y changes when x changes a certain amount of units.
parallel means they have the same slope (factor of x).
perpendicular (90 degrees) means x and y trade places upside-down, and the sign is flipped.
so,
10) neither. we have the slopes -2/1 and 1/1.
11) parallel. the slopes -1/2 and -1/2.
12) perpendicular. the slopes 5/1 and -1/5.
16) parallel. special case. all points that have x=4 and x=2. these are 2 vertical lines (parallel to the y-axis also known as x=0).
17) perpendicular. special cases. all points that have y=2 and all points that have x=5. this is one horizontal line and one vertical line, which makes them perpendicular.