The slope of the line given by the equation is -2.
When looking at the equation of a line in the form y = mx + b, the 'm' value is the value of the slope, and the 'b' value is where the line intercepts the y-axis.
In the equation we're given, y = -2x - 6, the 'm' value, which is the number attached to the x, is -2, and the 'b' value is -6. That means that the value of the slope is the 'm' value which is -2.
I hope this helps! Let me know if you have any questions :)