1. Which line is the flattest (or is less steep)? Why?

Question

y = 5x -6
y = 5x + 6
y = x - 3
y = x + 3

I thought it would be the last one since it has the smallest slope

Well, yes...but both the third and last equations have a slope of 1, and so have the same "steepness" (these lines a parallel to each other)