Answer:
1/3 is the slope.
Explanation:
First, we need to find the y-intercept of x + 4y = 20.
x + 4y = 20
Subtract x from both sides.
4y = -x + 20
Divide both sides by 4.
y = -1/4x + 5
Input 0 as x to find the y-intercept.
y = -1/4(0) + 5
Simplify.
y = 5
Now we know the y-intercept is (0,5). Now we need to include to find a slope that contains (0,5) and (3,6). We can use the slope formula:

(5 - 6)/(0 - 3) = m
-1/-3 = m
Simplify.
1/3 = m
1/3 is the slope.