I have done problems where I am given a contour map and I am asked to find a formula of a linear function but I am having trouble with this one. I found the change in $x$ over the change in $z$ but I can't figure anything out in terms of $y$. I have to give an exact answer and I have no idea how to get a slope involving $y$ besides estimating.
Am I missing something? Also sorry if I included a wrong tag or messed up the formatting, this is my first question on here.