#### Answer

(a) $3$
(b) $3$
(c) $-\dfrac{1}{3}$

#### Work Step by Step

RECALL:
(1) The slope-intercept form of a line's equation is $y=mx+b$ where m = slope and b = y-intercept.
(2) Parallel lines have equal slopes..
(3) Perpendicular lines have slopes that are negative reciprocals of each other (product is -1).
(a) Thus, the slope of the line whose equation is given is $3$.
(b) Lines parallel to the given line have a slope of $3$.
(3) Lines perpendicular to the given line have a slope of $-\dfrac{1}{3}$.