The equation of a line is typically written as y = mx + b where m is the slope and b is the y-intercept. Therefore, we must get this equation to look like a typical equation of a line:
9x + 3y = 5 original equation
3y = -9x + 5 subtract 9x from both sides
y = (-9x + 5)/3 divide both sides by 3
y = -3x + 5/3 result
Now we are in the form y = mx + b and we can see that m, the slope, corresponds to the value -3. Therefore, the slope of this line is -3.
Hope this helps!