Answer:
The answer is - 2
Explanation:
Equation of a line is y = mx + c
where
m is the slope
c is the y intercept
To find the slope we must first write the equation in the general equation above
That's
6x + 3y = 15
Make y the subject
Send 6x to the other side of the equation
3y = - 6x + 15
Divide both sides by 3

We have
y = - 2x + 5
Comparing with the general equation above
Slope / m = - 2
Hope this helps you