1 answer
(click or scroll down)
If line A is both perpendicular to line B and parallel to line C, it means that line A is perpendicular to line B and also parallel to line C at the same time.
Since line A is perpendicular to line B, their slopes are negative reciprocals of each other.
Therefore, the slope of line B would be negative reciprocal of the slope of line A, which is \boxed{\text{negative 5 over 14}}.