For the x-intercept the coordinate will have (x, 0) -- meaning that y = 0.
For the y-intercept the coordinate will have (0, y) -- meant that x = 0.
To find the x-interecept the y-value will be:
-3x + 4(0) = -12
-3x = -12
x = 4
Thus this line will cross the x-axis at the point (4, 0).
To find the y-interecept the x-value will be:
-3(0) + 4y = -12
4y = -12
y = -3
Thus the line will cross the y-axis at the point (0, -3).