The line crosses the y axis at y=-2. That is the y intercept.
And as for the slope: when the line goes down by 2, it goes to the right by 6. That is a "rise" of -2, and a "run" of 6. Slope is written as rise/run, so the slope is -2/6.
The easiest form for the equation is y=(slope)x + (y intercept).
Using the numbers found, the equation for this graph is
y = -2/6x - 2.
