yg bisa tolong jwb ya..

a) 5x-9-(7x+15y)
5x-9-7x-15y
= -2x-9-15y

b) 5x-3y+7-(5y-3x-4)
5x-3y-5y+3x+4+7
=8x-8y+11

c) -x²-6xy+3y²-(5x²-9xy-4y²)
-x²-6xy+3y²-5x²+9xy+4y²
= -6x²+7y²+3xy