Re-arrange so y is subject of formula:
y = -6 - 3x
y = -3x - 6
y = mx + c
c is y intercept and m is gradient (slope)
so, slope is -3, y intercept is -6.
To find the x intercept, you need to find what x is when y is 0, so substitute:
0 = -3(x) -6
Re-arrange
6 = -3 (x)
6 ÷ -3 = x
- 2 = x intercept
so y intercept =-6, slope = -3 , x intercept = -2