please is there anybody who can help me to do my assignment about sums and differences of a rational algebraic expression this is the problem.... x^2/x-y - y^2/x-y=? another is 3y/3y-5 - 5/3y-5=? another is 10/x-3 - 2x+9/x-3 + 5x-7/x-3 please answer it.......

You must have meant

x^2/(x-y) - y^2/(x-y)
= (x^2 - y^2)/(x-y) , you had a common denominator
= (x+y)(x-y)/(x-y) , difference of squares at the top
= x + y , x ≠ y