If X:: y = 3:4, then the value of 4x-5y / 4x + 5Y is?

If X:: y = 3:4, then the value of 4x-5y / 4x + 5Y is?

x:y=3:4
4x=3y
Original formula = 3y-5y / 3Y + 5Y
=-2y/8y
=-1/4