Explanation:
Pay attention to the slopes of these lines. The slope is the value stuck to x.
How to know if lines are perpendicular:
The slopes are the negative reciprocals of each other. This means that in fraction form, their top and bottom are switched, and their sign changes from pos-->neg or neg-->pos.
Ex of perpendicular lines:
y = 3x + 2 AND y = -1/3 x + 4
y = 2/3x + 1 AND y = -3/2x + 1
Not perpendicular example: y = 3x + 1; y = 1/3x + 2 because sign not changed.
How to know if lines are parallel:
The slopes are the same.
Ex: y = 5x + 12 is parallel to y = 5x + 300
SPOILERS
In the question given to you:
Lines a and c are parallel because they have the same slope, 8.
Line b is not perpendicular to a and c because its slope sign is not negative to a and c.
