slope in respect to an equation help

Consider two straight lines L1 (y = 2x +1) and L2 (y=x).

a) What is the slope of line L1 in respect to line L2?

b) What is the equation of line L1 in respect to line L2?

NOTE. Think that the original xy co-ordinate system has been

rotated in respect to the origin so that line L2 defines the new

x-axis x´ and y´ is the new y-axis!

now i know the slope of line 1 is 2 and line 2 is 1. im not sure if thats the kind of answer they want for part a of the question. and part b im not sure at all what they are asking for. PLease help me understand this sort of problem.

thank you