y= 3x +14 (a)
y=-4x (b)
Replace the value of y (b) on equation (a), and solve for x
-4x = 3x+14
-4x-3x = 14
-7x = 14
x= 14/-7
x = -2
Replace the value of x on any initial equation and solve for y:
y= -4 (-2) = 8
y=8