The line is:
Which is equivalent to:
Thus, the slope of the line is equal to -3/4
a) Every line parallel to that one has the same slope, then the answer is -3/4
b) On the other hand, if m_1 and m_2 are the slopes of two perpendicular lines, then:
Therefore, since the slope of our line is equal to -3/4, the slope of any line perpendicular to that one is:
Hence, the answer is 4/3