You must do work presented inside parentheses first. Thus, do this first: (-5-7).
You can't. If you think about the straight line on a graph, those numbers
describe a single point that the line goes through, and they don't tell you
anything about the slope of the line, or where it crosses the x-axis or the
y-axis. So I don't think you can tell the constant of variation from one point.
I would say direct because the more gallons of gasoline used, the bigger the cost.
