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 think it's the last one!

Parallel lines have the same slope. The first two are parallel lines with the steepest slope; the last two are parallel lines as well and would both fit the answer to your question.

Answer 1

y=x+3