The general form for a straight line is y = mx + c where m is slope and c is y-intercept.
Two lines are perpendicular when the product of their slopes = -1
Given line 3x - 7y - 14 = 0, its slope = 3/7 and y-intercept = -14/7 = -2
So a line perpendicular to the given and has the same y-intercept is
y = (-7/3) x - 2