Answer:
Perpendicular lines have a slope that is the negative reciprocal of the given line.
For example, if a given line has the slope 3/2, the the perpendicular line would have the slope -2/3.
For the given line: y = 4x - 7, the perpendicular line would have a slope of -1/4
There isn't enough info in the question to determine the y-intercept. Literally, any y-intercept could work and the line would still be perpendicular. Is the line supposed to pass through a certain point?
Your answer would be something like: y = -1/4 x + b
b is the y-intercept...if your question paper is multiple choice, choose the answer with the slope of -1/4. If it's supposed to pass through a certain point (x,y) replace x and y with the values in that point and solve for b to get the y-intercept.