Given:

The y-intercept is the point where the line crosses the y-axis, at this point the x-coordinate is equal to zero. To find the corresponding y-coordinate, you have to replace the equation by x=0 and solve for y:

Divide both sides by -3

The y-intercept is (0,-4)
The x-intercept is the point where the line crosses the x-axis, at this point, the y-coordinate is zero. To find the x-coordinate of the x-intercept you have to replace the equation with y=0 and solve for x:

Divide both sides by 4

The x-intercept is (3,0)