Question

How do you find the constant of variation when y=-(2/3) and x=3

Answer 1

$y=-\frac{2}{3};\ x=3\\\\kx=y\\\\3k=-\frac{2}{3}\ \ \ \ /:3\\\\k=-\frac{2}{9}$

Answer 2

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.