2（x+y)-2/3（x-y)+1/4(x+y)+2/3(x-y)
=2(x+y)+1/4(x+y)-2/3(x-y)+2/3(x-y)
=2(x+Y)+1/4(x+y)
=(2+1/4)(x+y)
=9/4(x+Y)
不懂的欢迎追问,如有帮助请采纳,谢谢!